My cats came apart in my 1989 SHO and never gave a code or anything else. But it would bog down on high RPM and would idle and run normal until I got on it. Never rule out the stupidest thing as it may bite you in the butt. Took me quite a while to figure it out. Finally bit the bullet and...
Look closely at the cover on the front of your transmission. The ford place replace my clutch and pressure plate and they did not inspect anything. They did not install it correctly and it wore the cover that the throwout bearing slides on. This part wore and caused a clutch failure exactly...
Also inspect the output shaft guide that the throwout bearing rides on. It ruins a clutch for me and ford installed the clutch and did not find it till the 2nd clutch was installed.
Before you go too much further you need to check the cats as they will break apart inside and not let the exhaust get out and it will cause backpressure and cause the engine to run hotter. Also you may be loosing fuel pressure from a clogged fuel filter or from a weak fuel pump. On all the early...
On my 89SHO I had the cats to come apart and it cost me power. I removed the cat pipes and cut the top of them open and gutted them and welded them back up and got my power back. Ran good till I got rid of it. Have found many 89's that have had bad cats.
I have owned several 89 sho's and on two of them I had trouble with the fans after 100,000 miles. I took the fans apart and put new brushes in and it fixed my problem. The brushes were worn and I could not find brushes. I went to an outboard motor shop and bought the correct hardness of brushes...
Take a torch and heat them really hot but do not melt them. It anneals them and makes them soft again so that they will seal. When you heat them they swell and soften up and then they can be used over and over.