Truck power loss

I assume here that the truck otherwise runs fine, but you have lost horsepower thru loss of compression. Let me know if that is incorrect. In order to regain compression you will need to hone the cylinders and replace your piston rings at the least. You should regain some lost compression. If you want to spend a lot more money you can further increase horse power by over boring the cylinders, increasing piston size, increase carburetor and intake manifold size to allow more fuel and air mixture into the cylinder, add a performance cam to handle the new high performance pistons, and add higher flow exhaust, etc, etc.

Yet another excellent, articulate and accurate answer jonny. Only problem is if you by any chance live in Calif., don't change exhaust. It's "tampering' and will never pass smog=never be able to register. That 1991 4.3 has single port throttle body fuel injection