I got 2 problems and don't know if they are connected. (1) Usually after the truck warms up, it has a surging/ pulsing idle and sometimes the truck itself will surge forward and stall out. I've replaced the IAC, plugs, wires, cap, EGR, EGR solenoid, Coolant sensor, and vapor canister. The spray looks good from injectors and I've looked for leaks @ the TBI base. Just recently rebuilt the fuel pressure regulator...I've got no idea....(2) When I take the gas cap off it makes a loud whooshing? sound. I know most tanks do that to relieve pressure, but seriously...It's loud. Enough of a vacuum to pull in the gas cap. Replacing the vapor canister did help this, but it's still present. Any help would be greatly appreciated...

 

Have you tried just replacing the TBI base gasket? It's a cheap enough part and easy enough to replace.

Are there any codes present?