my new truck with no power....need help.4.3 v6 4x4 blazer

[chevy power]

i bought this truck thinking it was not a major problem, it idles just a little rough. however i can drive it all around the little side streets and you think nothing wrong with it..then try to go main roads if you baby it it will run great, try to step on it a little feels like something holding you back..( just like a bad converter acts) however this truck has a brand new cap, rotor, plugs, wires,air filter, fuel pump and filter, from converter to rear bumper all new exhaust. new EGR valve.and a map sensor here is the catch....runs better with map sensor unpluged plug it in truck stalls....then will start hard and run way worse...unplug the map runs better just a little rough...map sensor is also new.....person i bought it from put in the fuel pump and replaced a section of the fuel line with rubber lines....and what a mess looks like they are all crossed and maybe hooked up wrong at the fuel tank....could that be??????? would it run at all if they were crossed? on the freeway can go about 8 miles then its on the side of the road...wait 10 secs and start it and go...hmmmm....any help would be great......92 blazer 4x4 4.3 v6 TBI W series not a vortex

[orionjunky]

I have a 4.3 vortex. I don't know if this will help you out or not but, I had the same problem. I had just changed the plugs and filters. I thought it was the MAF sensor, but upon closer inspection I had an big air leak in the intake between the MAF and the engine. This was causing pressure problems. If I let it idle it was fine. If I reved the engine it stalled for a sec but then caught up running rough. If I put it gear and let out on the clutch I had to gun the engine to keep it alive ande play the clutch to get it moving. Once it was on the road and back down closer to Idle RPM's it ran rough but ok, as long as I did not rev the engine. You might have a smaller air leak somewhere in the intake.

[smokey041369]

check pcv valve check the throttle position sensor tps