Sorry I'm 10 months late with this replay. Somehow this thread slipped through my subscription filter. With that said, I've thrown countless thousands of dollars into Porsche 951's (a.k.a. 944 Turbo) since 1993. I was a tier 1, powertrain electronics Supplier to GM and knew of the Pontiac demise prior to the general public. As the collectors were scrambling for GTO's, I committed to buying one of the 1st 100 (non-sequential vins) Captured fleet evaluation Coupes. It became available in May 2010 and had accumulated 15,000 miles. I'd never driven a Solstice Coupe or vert of any type but my closest friends in GM Powertrain told me the of the GXP's vast, untapped performance potential.
At this time, I was still in possession of my "LAST" Porsche 944T which had over $10k in suspension mods over and above the highly sought M030 option and $15k in the engine to achieve 350bhp. This is arguably the best handling production car ever built. The GXP Coupe was located at a Wisconsin dealership some 700 miles away. Prior to picking up the Coupe, my GM Contacts recommended the GMPP Turbo/SW upgrade so I had the dealer install it prior to picking up the car. So I've got a double disadvantage, I've never driven a GXP Convertible or Coupe with factory HP/TQ and the Coupe came equipped with FE3 Suspension.
Now that you've got a clear understanding of my Solstice background, I'll try and answer your question regarding the backbone and rigidity of my Coupe. When I left the Dealership in Wisconsin, I felt a little claustrophobic and vision confined. The claustrophobia was gone after the 1st 100 miles and the blind spots remedied with a stop at an Autozone and some 1" concave stick on mirrors. Finally feeling comfortable driving the car, I looked for some non interstate options to see how the car felt cornering, braking, etc.. Breaking was good, handling was, at best, marginal.
Once home, I was immediately on the phone with my friends in GM powertrain and performance division. That conversation led to an immediate order for a ZOK Suspension package, a Trifecta Tune and Eibach Springs to lower and stiffen the suspension. I gave Dave a call at DDMWorks and scheduled installation of the suspension upgrades as well as his mandrel bent IC Tubes. By pure luck, I was looking for REAL Tires on the Tirerack site and saw a set of 20"x8.5", one piece aluminium wheels on closeout at $75 each. They had the correct bolt pattern and offset so I made some quick measurements and ordered the wheels and Conti Extreme Contact DW 275/30/20's on all 4 corners. These were installed on receipt with no clearance issues and marked improvements in cornering and noise. There's a lot of negativity on the forum regarding 20" wheels so all I will say is "bring it on, stopping distance, auto-cross, 1/4 mile or full fledged track", I'll let the car speak for itself. I then flashed the Trifecta tune atop the GMPP upgrade. Wow was my only thought.
At DMWorks, Dave and crew made short work of the suspension mods which lowered all 4 corners by 1 1/4" still with no rubbing or Clearance issues. Dave then asked me if I was interested in a backbone. Not knowing what improvement I should expect from the backbone, I drove it before and after. There was a noticeable difference in the cars perceived rigidity and the Coupe was now equal to or better than my "very expensive" 944 Turbo S.
Dave then proceeded to take me for a ride in the 1st GT2871 Turbo upgrade car he'd just finished and once again all I could say was Wow! I placed the Porsche on Auto Trader the next day as I had already accomplished superior performance gains in the Solstice with a ten cent on the dollar investment as compared to the Porsche. With a small percentage of the money from the sale of the Porsche, I called DDMWorks and gave them a deposit on a 2871 upgrade as well as ordered a Solo Free Flow cat and exhaust.
The 2871 with an AEM water/meth kit, Solo Cat/exhaust and DDM's new Latin Venom front cross brace were installed in June of 2012. Depending on the Air Density on any given day, 400 dyno'd whp are achievable. My GXP Coupe now sits in the company of Z06's and pulls over 1.1g on the holy 200ft diameter Motor Trend test setup using a G-Force Monitor. I'm really at a stopping point with HP and TQ until I strengthen the internals (Rods, Pistons and Valve Springs). Getting current power to the road, even with the sticky 275's, is an issue. The rear will support 285's so I may end up with a staggered tire set when I replace the current 275's. A little over 2 years ago I'd have laughed at anyone that told me I'd have to nurse the throttle on a 2 liter turbo through 1st, 2nd and sometimes 3rd gear in order to keep traction.
The remainder of the 944 Turbo proceeds went into the purchase of a 1996 BMW 840 Ci. This wasn't something I was looking for but a close friend found himself in a situation where he needed to part with the BMW. It is an awesome car and I had full intention of making it my daily driver. Now if I can just find a way to walk past my GXP Coupe and actually get in the Bimmer for daily driver purposes, I'll have the best of two worlds. Thus far, I've only been successful about 1 in 4 times of making it to my daily driver.
To get back on topic, buy the DDM Race version of their backbone and the Latin Venom front cross brace. You will not be disappointed.
2009 GXP Coupe, Black, GMPP Stage2, Sumitomo HTRZ III Rear 285/30/20,Front 245/40/20, Dejon CAI, Eibach Pro Springs, ZOK Bars, DDM IC Tubes, DDM Extreme 1/2" Backbone, DDM Venom Brace, Solo Hi Flow CAT and exhaust, DDM Dual Gauge A Pillar Pod, AEM Water-Meth w/AEM Gauge/Failsafe
, AEM Tru Boost, DDM Oil Catch can, GT2871 Turbo w/ Synapse BOV
, OBDLink MX Bluetooth Transceiver, DashCommand,ScanXL Pro, Virtual Gauges w/Real Time Data Logging,Recaro PROfi SPGs