On my 99 tahoe. 5.7 2wd. Misfires when I get on the pedal . Spudders when I floor it. Feels like it's going to shut off when coming to a stop. Tune up just done. Wires cap and rotor and plugs. Revs up fine while in park. I did notice water coming out the exhuast manifolds when I removed the exhaust pipes to replace the tranny. I'm thinking the head gaskets are going bad and the cylinder pressure is escaping. Doesn't over heat but I've noticed the coolant has been going low every other week.