Slow acceleration
 

I'm experiencing very slow acceleration from stop. Started happening about a little over a week ago. It's at the point where I could hear the engine revving and I wasn't moving so I thought my wheels were just spinning on ice. I think it hits near 3K RPMs before I actually start moving. Also, if I let off the brake while idling it hardly moves forward if at all, not like it should while in drive.

Brand new plugs and wires. Coils, ICM tested good. New crank sensor. LIM UIM gaskets replaced recently.

I do have a lot of exhaust escaping from the rear exhaust manifold behind the engine. Definitely need a new donut gasket. Would this cause slow acceleration though?

Hmm, you could have a severely clogged cat. That would be my first guess. I'm sure others will chime in.
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I'm leaning towards trans if I am reading you correctly. Check your fluid level after a complete warmup on level ground. Also smell the trans oil. Does it smell burnt? Is it brown or reddish?

Sounds like a torque converter getting ready to vacate the car. There is a cleaner and conditioner available for some parts stores, I picked up some from Canadian Tire. One bottle is a cleaner, the other is a conditioner. Dump the conditioner in the tranny, take her out for a spin. Bring it home, dump the tranny pan, change filter and inspect the magnet in the pan. Lots of metallic pieces is not good. Bolt the pan back up and fill it to the full mark with the conditioner added. Keep in mind that tranny fluid is checked with engine running and on parked on flat surface. Some valving may be stuck and this may help. If it is a torque converter it is going to be a tranny rebuild.

If it were a torque converter wouldn't that affect it at all speeds? I just had to drive 150 miles from Indy to Valpo and it ran and accelerated beautifully at all speeds except from initial stop. In fact, right when I was about 5 miles away I hit a bump and my headlights went out. So I did BillBoost's stomp on the grounds method. It didn't work, sorry Bill, but then I put my foot up into the area directly behind the fusebox, lights came back on and it seemed like it ran better (not perfect) from start. I just drove the last few miles with my foot pushed up below the dash. Maybe it was wishful thinking. So I obviously have some bad connections in there. With that being said, would there be anything in the driver's dash area that would affect this?

My initial thought was tranny as well, but it seemed to come up at the same time as all my electrical issues. I have another thread on those here https://www.gmforum.com/1992-1999-91/fuses-286899/ .

Issue was resolved by rewiring driver's side beneath the dash.

See:

https://www.gmforum.com/showthread.php?t=286899

Sounds like a ton of work, glad it worked out for you.