The Truck: 98 chevy 1500 p/u4x4 350 MPI automatic trans

The Problem: so I recently had to replace my Lower intake manifold gaskets as they were so degraded.
they fell apart in my hands after succesfully putting the top of the motor on and putting everything back right,
I test drove. Everything works great as im driving through the city on the interstate however its much different.
usually above 50 mph when you foot is just holding steady throttle there is an intermiten banging that occurs.
It feels just like when the lockup on the torque converter goes, i know that beacause earlier in the year I that problem.
so it bangs then if you add throttle however keeping it in overdrive then roll off throttle completey BANG it does it again.
Then it drives fine for 1/2 mile 1 mile or 5 add throttle bang. let off fast bang to further my frustration the SES light has not come on.
and the fuel trim and igintion timing is dead on and it only does it "sometimes"

The truck never once made this noise or sensation through the truck one time until the intake came off my diagnostic led me to this.
Fuel to rule out bad fuel I ran fuel tank stabilzer through the tank when i filled up with 10 gallons. Since it does it most with certain parts of throttle position i began thinking air/fuel bad TPS sensor maf/map? probably not since it doesnt do it constantly. I dont think its spark because it only really does it at certain points of throttle but im notA professinal technician

thanks Nick