Help with gettin rid of some codes

[Camaroman1221]

i have a 2000 camaro with pacesetter headers, no cat, cold air intake and a flowmaster catback, i have been having a problem where my computer with throw p0172 and p0175 which are system rich code. this didn't start till i took my cat out and put headers on, now i did them both at the same time so i don't know if one or the other is causing this or nether. lately i have also notice a stumble from the motor and 1500 rpm's in 5th gear and this is the only time it does it. it kinda hesitates like its not gettin fuel, now could these problems be linked to a bad injector or could somthin else be causin this, the motor has about 120,000 mile and the rest of the drivetrain has 92,000 mile