1990 Chevy Silverado not a loss of power but not going thre

OK so when I start up my truck it start up at the turn of a key runs nice idles fine and sounds good when I rev it the rpm go up smoothly it runs like there isn't a problem but when I put in it the D with the O around it and the regular D and drive down the road the 350 will not rev over 1500 rpm like for example in first gear it revs up to 1000 kinda stumble then move to 1500 then a the last second before it shifts the rpm jumps a little like from 1500 to what looks like 1700 or 1800 then it shifts then the rpm drops down to 500 rpm then slowly builds back up it does this threw all 4 gears now when I put it in 1 then I can rev it up to 3000 rpm then I shift it in to 2 then do the same thing then shift it in to D then I cant bring it above 1500 again also my exhaust sounds a little different kinda like a sprinkler but a little faster pace and it gets faster with the rpm by the way I had dual exhaust and I don't know how old the setup is. I changed the plugs wires cap rotter air filter fuel filter and fuel pump the sending unit was also replaced and checked and rechecked the timing (unplugged the est wire first) I redid the seal around the intake manifold I have no idea what the problem is I just got it and im dieing to hot rod it can you please help