I Just Got a 92 z28 350 camaro problem is over 70 mph it starts to run rough like its missing and it does it in park over 3000 rpms any ideas

i think its stock but am not sure

maybe ignition? possibly plug wires or cracked cap or i was thinking the harmonic balancer

 

What's the first thing you do when you buy a car?

I don't know about you, but I have a simple checklist.

1. Change all the fluids in every place that has them (oil, coolant, trans, rear end, etc.) making a point to observe what's in the rear so we don't get victimized with yet another pointless "what gears do I have" and "do I have a posi" post
2. Do a brake job
3. Replace the plugs, wires, cap, & rotor
4. Fix any leaks
5. Start troubleshooting whatever is still wrong with it
6. Go to work on beauty items like lining up the fenders and hood and such, and de-rattling the interior, fixing water leaks, and other trim stuff

Rather than jumping directly to step 5 before completing step 3, follow the steps IN ORDER; after completing step 3 and 4, and then if you're still stymied in the middle of step 5, come back and we can work on it.

 

any (or all) of the above-- agree completely with the list of "gotta-do firsts"
methocically work the list and the problem will reveal itself more often than not.

don't overlook the fuel delivery in a rush to judgement either-- low fuel volume will show itself only when the demand is high (higher RPM)

as for the list: can you really de-rattle the interior and stop water leaks?
I guess on Maslov's pyramid I haven't reached that level yet!