850 double pump issues HELP!!

ok first off i got a used 850 dp and put it on a 360 thats ehh mildly built. and when i put a load on it to launch at the strip it just spit and died. ok so thought it needed rebuilding so rebuild it and same prob. well i bought a new base plate, main body, metering blocks and fuel bowls so pretty much a brand new carb well i started at 80 and 81 jets same prblm went down one by one till 70s same thing went up to 90s and belive it or not it took SOME of the stumble out but not all and ran way to rich..basicly what im asking is there sumthing im doing wrong?? i have the 50cc accelerater pumps do i need to go larger or what? i borrowed a 750 dp with 80 and 81 jets in it and it runs great is the 850 just to much for my motor or am i just not tunning it right?? im running holley blue electric fuel pump and about 7 fuel press. if you guys know something i dont please tell me if you need any more info let me know thanks