The thing is, while it was the cat being deformed and blocked in the end that was hard to diagnose, at the start it could of been any number of problems. But while all the other parts listed were changed the damage to the cat had already been done. I think that the cat was a symptom of the problem, Not the cause but this is just my $0:02c
Reading through the first post, Im thinking the TPS isn't setup correctly in the ECU. Then Im thinking the Map sensor isnt plumbed up right. Who could have guessed it's the cat... bad luck mate, sorry to hear you are parting it out!
Actually, the problem is just the limits of the OEM map sensor
This sensor goes 5v @ 10~12psi & the S/C in question will exceed this...
My guess is the car was likely tuned at WOT & not at part throttle high rpm.
Chances are the tuner didn't notice the MAP sensor going 5v & the car made it to the road
Dyno sheet says WOT the car makes good power & all is well... etc etc
But the owner uses part throttle & revs it a bit to avoid the annoying BOV sound that these set-ups have...
MAP sensor sees 5v but at part throttle... yet the fuel map delivers the fuel required of WOT...
Say bye bye cat...
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