My 98gt has been running great this season however recently I noticed some bogging and backfire issues which seem to be becoming progressively worse. I took the car out for a spin tonight and got on it down an off ramp and noticed everytime I went to shift in high rpm the car would backfire/studder and bog really bad into the next gear. Car has a complete PI engine brand new plugs/new fuel filter, red monster cop conversion (which has worked great), Brand new upstream O2 sensors. I suspected that the fuel pump may be going out as it had seemed a bit too noisy at times. I'm sure it's still the factory one 145ks on it. I've order a new fuel pump (walbro 255), We'll see if that clears it up; however this has me stumped as it has been running hard as hell for me tell now.