so i have a 05 r53 with only one modification i have an invidia cat back exhaust with the middle resinator cut out. the problem i have is ever since i cut the resinator out the check engine light came on. now just to let everyone no i use the car everyday and it seems to run fine iv ben puttting in regular gas like a dumb *** but should that affect the car, if anyone can help with this problem or y that code is on that would be great thanxs

 

p0172 is a code that says the system is to rich. Check your fuel supply. or your on board diagnostics for the code. Could also be a bad or going bad oxygen sensor.You should only use Premium Gas of 91 or higher. Fill up tank with good gas and put a can of SEAFOAM in the tank and runit for a couple hundred miles and see if this helps. If this dosnt work try putting a spacer in back o2 sensor or replace the resonator.

 

ok thanxs very much ill let you no how that goes