It feels like a clogged catalytic converter, but does not happen all the time.
When this happens the car will idle kind of rough, and when I hit the accelerator fast it will stumble and hesitate really bad from 2000 to 5000 RPMs, if I press on the accelerator slowly I can bring it up to about 4000 RPMs with no stumble.
Today I noticed that the cat was glowing red hot, so now I probably have to replace it, However I would like to find the original fault so the new cat does not go bad.
The car is an 88 with about 145k, and I don’t know much about the service history of the car.
Any ideas thoughts would be greatly appreciated.

Thanks,
Mike G.

If the cat is cherry red, the car is most likely dumping fuel. It could be because of a number of things.
Bad o2 sensor, making engine run rich (is the check engine light on?).
Bad ignition wires, causing stumble like you said, unburned fuel going into cat.
Start with these two and let us know how you make out....

I'm gonna try an o2 sensor and see if that takes care of the prob.
BTW the check engine light is on and my scan tool only does OBD2 so i have no way to check the code.

Thanks,
Mike G.

A faulty air flow sensor can cause these symptoms. Just a thought

Now the car will not start when its warmed up, I have a new set of plugs,injectors,o2 sensor, no restriction on the cat I'm going to re-check the fuel preasure today.
How common are the DMEs for probs.
Thanks,
Mike G.

Have you checked the fuel pump, mine used to stutter till it gave up completely

My 1989 735i had a similar problem. After a lot of checking, tightening, cleaning, head scratching, etc. I checked out the rubber connection between the air filter housing and the MAS. The rubber looked okay, but there were small cracks in the bottom of most grooves. I replaced the rubber part and the problem went away. There must have been some small cracks that went all the way through. Part cost $25 from Bavarian Auto in NH. Glad I checked this first since a new sensor costs 100's of $$$:)

Lots of good suggestions so far. You may also want to pull your distributor cap and take a look underneath. A cap with cracks, carbon tracks, and a worn out rotor could cause all of your symptoms. It's something you can check out without buying parts first.

I just went thru the same problem. Started with checking fuses (fuel pump). It did get better but eventually returned. Check your hoses and radiator cap. I had to replace the distributor cap b/c it was cracked and got new plugs at the same time. Checked the idle valve and had it adjusted. I had some other work done (power steering pump) but the problem has stopped.