About a month ago I replaced the head gasket, had the top sanded and compression tests are just fine.

When reassembling the car wouldn't start, after some troubleshooting I found it to be corrosion on the injector causing very bad contact, cleaned them up a bit and the car startet.

But too often when driving it suddenly goes from good to running crap, it hunts and rpm vary from 800-200, sometimes it even stops, the strange this is, if it happens on the highway, and I push the trottle to the floor, it will accellerate almost as normal, but when I let go a bit, it starts to hunt, I have to keep it out of overdrive (force a high rpm) to keep it going.
But if I put it in neutral and let it idle (at speed) for 10-15 sec, almost every time it will be back to normal - but only if I let it idle, not if I keep it going at high rpms.

I have tried numerous times to clean the injector and harness, changed the plugs several times, any idea to what other things to check?

 

Seems like you have a vacuum leak. I changed one fuel injector in my 92 SE a couple of months ago. It has the symptom of your car. Turns out the injector was not sealed properly. So I had to re-install the injector with a new seal. Also, do not force injector when install it. Use engine oil to lubricate so it goes in smoothly. Hope this helps.

 

 

Another route would be to upgrade to 93-94 VG rail rail, injectors, injector harness, intake adapter plate and throw that ole school injector wiring in the scrap bin.....The bellows are all cracked and leaking by now leading to constant injector pin corrosion...I personally couldn't stand it anymore!