Hi,
I was having a stumble over 7000 after doing my mods, so i tried redline injector cleaner, and just finished installing the rp high flow denso fuel pump. I took it out and it first it still had a hesitation, however after a few good pulls to redline it started to smooth right out. Is it possible that with only intake downpipe and exhaust that the pettit ecu is running really rich at idle and fowling up the plugs?? and then after a good couple of pulls the plugs are cleaning up and that's fixing the hesitation??? Please let me know what you think. BTW the plugs are 9's all around and have less than 1000 km on them.

Andrew Wojteczko,
93 RX7 R1

 

Sounds like your plugs were going. As how rich the pettit runs iam sure they are fouled.

 

i had the same problem it was a miss at high rpms a hks twin power solved the problem for me.

 

Why don't you pull the plugs and take a look?