92 Civic HB VTEC swapped NEED HELP!

I have a 92 Civic CX(1.5 8v), swapped to a 93 Civic EX (1.6VTEC). The car runs like a champ on the lower cam, but as I top out vtec about 1000rpm before revlimit (7100 I think...) it starts to pop and skip, and my tach jumps like crazy. I unhooked the tach and it is less noticeable, but it still does it. The car has the basic bolt ons, an exhaust, an intake, 9mm wires. I already tried a different distrubutor, different wires, cap, rotor, everthing I can think of. DOES ANYONE KNOW WHAT IS WRONG, I REALLY NEED TO FIGURE THIS OUT

Thanks, Rya

 

dumb questions for you:

1. are you running nitrous? it affects ignition.
2. did you swap ecu's? the ex ecu has different red line. if you're
running up against the rev limiter on a cx ecu, symptoms are exactly as
you describe.
3. is the timing belt adjusted properly? slop in the belt means cam
timing is wandering back & forth all over the place. with the extended
overlap on the high rev cam, that can cause problems.
4. you say your [presumably after-market] tach affects this situation.
what other electrical mods do you have? electrical noise can easily
cause major issues.
5. are you running the stock ex ignition/distributor?