This might not be quite the same but i had 246awkw, then i got a decent front pipe, cut out the cat to 3 and a half inch exhaust.. From the exhaust place
i took it up the road, put my foot down & it was misfiring over 5000rpm.. Took it to my tuner, he eventually found it was my boost pipes.. He tried a couple of
new clamps on my std pipes but they weren't holding so then i had to get a new set of boost pipes..