shift problems

I have an 89 buick with a 3.3L engine. My car has problems shifting. It will shift at high rpm range. 4000 to 5000 rpm. After about half an hour of driving it will settle down to 3000 rpm. I need help finding out what the problem is. The pcm has been replaced at 189,000 miles and the car has about 199,600 miles on it.

The transmission appears to be slipping causing the shifting problems. You may want to try a can of Sea Foam trans additive to clean up some of the internals. Unfortunately, you also may getting to the end of the useful life of this transmission and you may need to replace it. Also if you haven't changed the fluid and filter lately start there and add the Sea Foam to the new fluid.

Should I use Sea Foam or Lucas. Which kind is better.