losing power

Air fuel and compression. I am betting your problem is one of those. Fuel fillers number one guess.

 

If you can get the first (primary) fuel filter off, pour it out where you can view the contents in good light. If it looks brown or watery or otherwise doesn't look like clean fuel, you probably need to replace that filter because you have recently got a bad load of fuel or have accumulated enough trash/water to kill your fuel flow through the filter. It's best if you have a small amount of fuel to top off the filter before you screw it back on (or the new one) and restart.

Also, you may have a "fuel observation bowl" somewhere. If so, does it look like clean fuel or brown water?

 

I would start with the fuel filters. I would go ahead and just replace them. If your engine is missing you could have water in your fuel or a bad injector. Changing fuel filters is about the least expensive thing you could do.

 

Maybe air filter as well - easy to check.

 

Take it to a Detroit shop.

 

I'll second that!

 

It would be cheaper to just change the filters and see if it makes any difference first and then take it to a shop if that doesn't fix the problem. Of course, a garage could hook up to your ECM and see if it shows anything else going on.

 

I only said take it to a shop because the op didn't sound like he even knew where the fuel filter(s) are. Not everybody has any mechanical apptitude, and are better off taking it to a shop and paying the piper.