General Maintenance & Repairs - Fuel / Spark issue? Needing help guys.

2000 Z28 A4
Slp lid

Been having a problem with the car stumbling / harsh loss of power. Thought by all the symptoms that it was a bad fuel pump because of it acting like that / still factory pump @140k miles and it started making a heck of a whine. Put a 255lph and the car drove and ran perfect for 100~ish miles and then all of a sudden same thing. There is no check engine light on, cats recently replaced, and does it worse with the more throttle you give it when it is acting up. I've pulled over. Shut the car off for less than a minute and started it and drove right back off with no problems. What in the world is going on?

This is my only means of transportation at the moment. Any help would be greatly appreciated.

sounds like a problem i had. space the icm off of the cylinder head with washers if you havent already. shbox.com has a writeup/how-to called icm cooling mod.

My car is a 2000 with an ls1. I don't believe it has an ICM. I'm just really up a creek right now. Its intermittent but when it doesn't wanna go I can shut it off and start it, it might go 5 miles again or it might go 50. The new fuel pump doesn't whine or make a sound, I just don't know where to start on this one.

my bad, every now and then i forget how to read