Any help would be much appreciated.
I have recently purchased an 86 Iroc Z..when I bought it, it was missing heavily when started and being revved in park. It was also very retarded when driven and missing badly.
I took a chance because it's in great condition otherwise and real clean.
Since then I have had the following replaced:

Fuel filter
Plugs
Dizzy cap
Rotor arm
Distributor module & pick up

I am due to collect the car from the garage tomorrow, and the mechanic states that the car is now driving fine and pulls lovely, but that it is missing under the throttle whilst sat in park.

Any ideas what might be causing this ?

Thanks in anticipation.

 

Oh...it idles fine. It's just when you put your foot on the pedal.