I just bought a 98 GT 4.6. It runs good and feels pretty strong. It has a ton of bolt ons and I'm leaning towards this being the source of my problem. The current mods are as follows. -BBK CAI -MAF (not sure what size but aftermarket) -Trick Flow 75mm throttle body w/plenum combo -BBK Piggy back style under-drive pulleys. -BBK Shorty headers -BBK Cat-Less H-Pipe (has all sensors) -Little single chamber flow masters Thats about it. Now the problem I'm having is at WOT at mid range rpms. It fells like a miss but random. Just a tiny loss of power for a split second a few times each gear. My gut feeling is it's starving for fuel. So I figured I'd take advantage of free code reading and printout at auto zone and this is what we got. Code P1443- evap can purge valve fault P0171- fuel bank one lean or rich condition P0174- fuel bank two lean or rich condition P0420- catalyst efficiency low-bank Alright, so I'm pretty sure I have a fuel problem most likely lean. Each code print out gives a brief description but I need some help understanding what the hell they are talking about. If she was carbed I'd tune her up and be good to go. I'm sure this problem is caused by the mods. Is all of this because there's probably no custom tune on the computer? What else can I do? Fuel pump? Injectors? Not sure where to start. Any help is greatly appreciated.