I've been having a problem with my 02 GT for a little while now and I cannot figure it out. Its been throwing codes such as P1131, P1151, P0174, and P0171 which are all lean codes. Why is it running lean? Also it idles real bad, it will surge up and then drop real low like its gonna stall out. I cannot figure this out, i changed the mass air flow sensor and the throttle position sensor and still having problems. I have a C&L intake, Trick Flow 75mm throttle body and plenum. I'm not sure if it has anything to do with my throttle body or plenum but it started when I installed them. If anyone can help let me know, thanks.