My 2007 GXP (86,000 MILES) has started throwing engine codes at me (P-0299 and now P-0420). Oddly enough it went into limp mode without throwing a code the day before the P-0299 popped up and then started up this AM with a P-0420. The Pontiac shop recently changed out the High Pressure fuel pump and I was thinking that they may have not properly attached some of the turbo hoses, but now with the P-0420 code I'm wondering if it may be the CAT. I've been running a High Flow Solo CAT since the first 5k miles, so do y'all think that it could possibly need replacement after 80k miles? Of course I have my OEM CAT, but I really liked the sound and low end torque the SOLO gave me.