Need some idle help

[chrisman_go]

Hi there, I am new to the Pelican board. I have a 91 C2 with an idle problem. I think the best way I can describe it is that the car sounds like it um, has cams- but it does not. The vehicle runs fine off idle, but when returning back to idle it has a distinct "chop" or "lope" instead of a smooth even roll. Sounds are worth a thousand words so I have included a small Youtube video of it doing its thing.
I have thrown a bunch of replacement parts at it trying to remedy this:

1. I have gone back to the stock chip
2. A new air meter
3. New caps & rotors
4. clocked the distributors & made sure the belt is not 1 tooth off
5. new Idle solenoid
6. new 02 sensor
7. checked for vacuum leaks

The only other info I have is that the car feels a bit down on power compared to other 964s. Perhaps a flatter power curve instead of a strong top end kick that other 3.6 have. The only mods ive done on motor is the chip, cat bypass and primary bypass.

Next I want to try new coils, try a diffrent DME, maybe a fuel pressure regulator?
So its expensive at this point, and Id like to ask for your guys' help for any further ideas on what could be causing this.
Thanks, Chris

here is a video of the "chop"- go about 40 seconds in..
YouTube - MOV01200

[Newsboy]

Have tried cleaning the ISV (Idle Stabilization Valve) ?

[chrisman_go]

I believe so, I didnt know the correct terminology I think I called it the Idle solenoid, but its the small silver canister on the top of the motor, I swapped that out.