I have a 95 Sierra sl 297,000 miles 4.3 stock it started surging at slow speeds and having to give it to much peddle to pull hills and gas mileage has been shot. It idles great no miss less than 20,000 on tune up fuel pump less than year old. What can possibly be the culprit for my problems. Any help will be greatly appreciated

Mass Air Flow sensor could be dirty.

If you plan to clean it, use MAF sensor cleaner only and do not TOUCH the elements inside of it. Then once you do clean it, disconnect the batteries, this should clear any saved fuel trim data.

My 4.3 has the tbi it doesn't have the mass air flow on it

Oh, that nixes that then.

What condition is the catalytic converter in? Is it throwing any codes?

No codes at all

Pull your 2 front O2'* and go for a drive. See how it drives after that.

Have you looked at the fuel trim,o2 values or fuel psi.Just a thought of some thing to look at.