My car is giving problem. Everytime I pass 6000 rpm the car starts to missfire/ stutter. The check engine light which is already on cause of the o2 sensor starts to blink. When the car is in neutral and you rev to 6000 rpm the car again does the same and the other speedomoter start jumping up and down.

I thought it was my distributor which was an OBD1 - just rewired
so I changed to an OBD2 but the same thing happens

The motor set-up is LS/Vtec - 99 Si Computer w/ 99 si harness.

Help if you can.