Throttle Mashing hesitation?

[JetForceF22]

Hello everyone.

I have a 1995 Silverado Z71 4x4 with the 5.7L 350 engine. (Need any more specs please ask)

I've done a lot of work to this truck, Engine mods include

-The ULTIMATE TBI mod (most of it)
-Adjustable Fuel Pressure Regulator (running 15-20psi, depending on outside temp)
-TBI "Swirl torque" 1in spacer plate
-Flowtech Shorty headers (3in collectors)
-Y pipe with 3 inch outlet, going to 3 inch high flow walker cat converter
-Single offset factory style exhaust outlet, also 3 inches
-Highflow Edelbrock 255lph (Roughly 66gph) fuel pump and new sending unit
-In cab fuel pressure guage
-New fuel filter about 6,000 miles ago

(aside from that regular maintenance oil changes pcv valve air cleaner ect ect.)



Okay my issue (which I was having BEFORE I changed the fuel pump and did the ultimate tbi mod and fuel filter and pressure guage) was I would mash the pedal, but it would sputter and almost die, then the transmission would down shift and then I had all the power back (but I wouldn't have any high rpm power, and would have to let off the gas to get the power) but the initial loss of power would almost kill the engine.

When I changed the fuel filter, the problem went away, shortly after that the transmission died, and I had it rebuilt a year later.

So now the problem has returned. Its not as bad as before (The sputtering before I changed the fuel filter- it would sound like the truck would go down to one or 2 cylinders before the downshift, and now its not quite that bad) But I'm experiencing the large drop in power when I mash the pedal, which should not be the case. I'm wondering if its the fuel filter again, because when I knocked the old sending unit, the sealing ring was completely covered with rust, and a small amount of dust/debris fell into the gas tank. There was really no way to get it out since there was still gas in the tank and at the time draining the tank completely was not a option.

*Edit* Also I have tested to see if the "hesitation" would also happen in 1st gear. Its like when I put the pedal to the floor, the truck doesn't respond right away, I get a large drop in the RPMs, then the truck comes back alive. Also I noticed that it does it when the truck is warm. The truck seems to run stronger when its cold, odd I thought it was supposed to be the opposite. Any help is appreciated.

Hope I explained everything clearly,
Thank you all in advanced for reading this and any suggestions is very much appreciated.