02 WRX stock dyno check
I purchased an 02 wrx about a week and half ago. I believed at the time it might have been modified because the muffler was done, it has an STI wing, STI badge, and STI shift knob.. But upon closer look, everything else is stock except the muffler. I immediately removed the STi badge.. that's silly.. But anyway it has 120k miles and I was curious about it so I had it dyno'd.
It was in Salem at Dan Judy's auto and Dan came down from his loft at the place once he heard a subaru and showed me his 02 with 420 hp and 3400 miles.. but that's another story. Anyway attached is the results. 178.5 max hp at 5800 rpm is not bad. But there's a flat spot between 4000 and 4500 that was unexplainable. Plus it seems to be misfiring or not running smoothly sometimes. The tech said he felt it struggling a bit while running the dyno on it also.
So they came to the conclusion that the previous owner never had the plugs done. Which also means that they probably (hopefully not) have not done the timing belt. Attached is the dyno, what you guys think? Can you explain the flat spot at 4-4.5 k?