just wondering if anyone has ecnounter backfiring problems on an Sti V2 RA all stock except for exhaust. boost comes on strong but backfire and hesitant after around 5k rpm

Had the following parts replace n tested to see if faulty even though there is no CEL coming on. All of these parts were replace to test:

- ECU/MAP/MAF/ignitor/boost solenoids/ignition coil/camshaft n crankshaft sensors/throttle body assembly/fuel pumps/sparkplugs

what could be causing the problem? it is not overboosting as we have check thru the boost guage

 

anyone??

 

Fuel filter?

 

have also try replacing fuel filter n still the same. will try replacing the whole intake manifold along with the injectors and regulator to check it again

 

have it checked on a wideband?

 

Could the O2 sensor cause this?

 

haved also done the complete intake manifold and replace the whole downpipe with an another and still back fire still the same =( have actually replace evrything and it still the same. there is no CEL code as well does anyone have any other ideas?