Completely baffled.
87 Z28 305/ 5 speed idles great, if you baby light foot it drives great, if you hotrod it drives great but NORMAL driving when you get up in the rpm band prior to shifting it jerks, shudders,
backfires till you either give it more gas and push thru it or let off and get below it. While its in tat throttle spot its violent.
Runs great all over no issues till it warms up then the certain rpm shudder starts.
So far in the last 60 days we have installed:
new tank
new fuel pump
verified correct fuel pressure
new TPS
new plugs, wires, rotor, cap, ign module, distributor
verified no vac leaks and correct vac amount
removed and had injectors flow tested on bench (no sure if they can "warm" test them on the bench) going to ask tommorrow.
new ECM and Prom

Any ideas?

 

You have so many "new" parts, any of them could be bad. Have you verified the new stuff?
You say correct fuel pressure, but what is it? What is it when you are having issues?

Would be interesting to see some data when it is happening. My guess would be either you are having MAF reading issues, 02 reading issues, or a timing issue. When you let off, you go into Fuel Cut mode for deceleration, when you tip in the throttle you get AE mode and if you give it enough throttle you will be in PE mode. Both of these are not actively adjusting the fuel mixture, but steady state is. Also, your timing table is load/rpm based.

Does this happen with the MAF unplugged?
What readings are you getting from the 02 Sensor
How does the BLMs look as you drive?
What does the computer think is the total timing when it starts happening.
TPS voltage during the issues?
How about your CTS reading? <---- big factor in the TPI programming