Okay, so my 93 si with 180k has a strange issue:

When its cold, it runs just fine. But after 5 min of running (shortly after the temp gauge gets to 1/2), there is NO power under 3500. Nothing.

I checked the timing. replaced plugs and wires. compression was between 205 and 225 for all cylinders (tested all warmed up).

this is really kicking my ***. Please help?!

 

I got the same prob. It could have somthing to do with the EGR valve also. you throwing any codes? you do a tune up?

 

Do one of two things:
1. Pull the intake manifold and clean the **** out of the EGR runners.
2. Leave the manifold on, remove the EGR plugs and spray carb cleaner into the EGR ports.

I prefer no. 1 though it's a bit more difficult. IMO you'll get a better cleaning.