help having high rpm issues

[TurboTA3.8]

well finaly my car is up to snuff and i get it on the dyno to do some tuning tonight just got a dynojet 224x thing is great

so anyway the first pull it breaks up so i change the plugs and gap them to .028 then do a pull it pulls great to 5800 then like noses over and breaks up the a/f went a little lean 12.6 but not enought to have the power nose over that bad this is at 10 psi boost coil pack and module are new and plugs are new and the wires are in great shape it happens at the same rpm i tryed it at 3 boost levels 10,15,20 same spot each time the springs are good big k motions head gaskets are good and it passed a 8 % leak down any one have any ideas is the stock ignition not up to par what are people with my setup using.

thanks
george

thank god 4 year project coming to a end

well it made 540 at 15 psi at 5600

 

[ijames]

Once the engine is misfiring or breaking up you can't trust the O2 readings, whether a narrow band stock sensor or a wbo2 like you have. The misfire dumps raw fuel and oxygen in the exhaust and some random, not necessarily reproducible amount of that will burn by the time it passes the O2 sensor. If you saw it start to go lean and you are as confident of the ignition as it sounds like you should be, I'd add some fuel.

 

[TurboTA3.8]

was the plugs i put in a new set of ngk's gaped to .028 and the car is fine

george