97 c2500 454 hissing bogs engine down a little

[97 c2500 reg cab 454]

So I have a 97 c2500 454 when I am driving at 30 to 40 mph it will start hissing and it bogs the engine down and I loose about 5 to 600 rpm I have brand new fuel filter spark plugs and wires. It's not the trans cause it does it half way through the gear. Lmk what yall think.