Issues after warm up
 

A friend has a 1986 NA that starts and runs fine but once it warms up, it would not rev more than 1500 RPMs. Any ideas as to what is wrong?

How did this come about? All of a sudden? Gradually?

Any other info?

Initially I'd be suspect of the DME temp sensor. It's the blue capped sensor just to the right of the water neck on the front of the engine block. It sends the temp to the DME to control fuel richness. it's an easy replacement and relatively cheap, too.