Okay i have a 87 iroc- z. I'm not sure weather it's a 305 or a 350. But it idles high in park and then slowly will come down to normal. And when I go into gear reverse or drive it starts missing and running really rough. I just replaced the cap, rotor wires and plugs. I set the timing where it needs to be. When I get in the high Rpms there what sounds like a loud vibrating noise from the engine. It is TPI also it kinda head tastes if I give it just a little gas in drive. There is no check engine light on and I checked any codes and it only gives me 12 witch iv read is all normal.

 

Did it run poorly before the ignition tune up? If so, test fuel pressure, check injectors etc

 

Yes it did. How do you test the fuel pressure and injectors. Haven't done that before.

 

you can do an Ohm test for the injectors. If you do a search on the site there are plenty of write ups on it. To test the fuel pressure you take the cap off of the fuel rail (passenger side, just behind the last runner) and put a fuel pressure gauge on it. turn the key to "on" and check pressure, then turn the car to run.
there are also ways to test the pump and rest of fuel system but IMO it doesnt seem to be your problem.