So on the highway, I decided to downshift to third and I noticed that the engine once it hits 4500 it won't go any higher.

As soon as I got home, I revved it while parked and then it would 5500 which is where it should be. Before this I figured that the car started running lean when it hit the higher RPMs but with it redlining when parked I'm stumped.

I ruled out the Mass Air Flow sensor because from experience if something is wrong with that it won't even let me rev past 2500 on other cars so I assume it's the same here.

Any ideas?

 

The amount of fuel required under load is much higher than what is required to rev out in park. Sounds like you might be running out of fuel. Check your filters and fuel pressure.

 

Could be valve float too, how many miles are on the engine? A compression test could tell you something too...

 

i just had the same prob with my 91, after i verified i was getting plenty of fuel , i checked the plug wires, then cap and rotor, coil , then the icm, after all of this was checked and replaced the stuff that looked like it could use it, i still had the problem so i tooked her to the muffler shop and had then but a new cat on it and that was the cause of my prob , good luck to u