losing power

['93 trooper]

Hello,
I have a '93 Isuzu Trooper 3.2 v6 with 155,000 miles, that is running bad. I've taken it to my local mechanic but he can't figure out the problem.
Suddenly one day my engine started to sound real throaty, and it started losing power. I can barely get it up to highway speed, and can't maintain speed up a hill. If I press on the accelerator too fast the engine will rev up, won't produce power, hesitates, and it sounds as if it's about to backfire, and there will be kind of a clunking sound. Also, the check engine light sometimes would come on when I depressed the accelerator, then turn off when the engine comes back to idle.
I've had a scan done on the vehical and these are the error codes;
32 egr, and 43 esc.
A compression test on the cylinders was normal.
The catalytic converter was removed, inspected, and deamed normal.
The intake manifold, plenum, and intake plenum gaskets were replaced.
The spark plugs, and ignition cables were also replaced.
If anyone has any ideas, I'd love to hear them. Thanks.

['93 trooper]

Anyone?

[amigo-2k]

plugged cat.

[ridinghigh]

Had a similar problem with my 94 3.2 dohc during trip through Rockies. Took it to a mech who said spark plugs were sparking into engine block - a potential prob with this engine. Put in new wires and filled with dielectric grease to esure spark went to tip of plugs where it belonged. Drove like new afterward.