Ok, had my tranny rebuilt and put a shift kit in it, and recently replaced the MAF sensor, and it isn't throwing any codes - and it truly snaps my neck, but one problem wasn't able to be fixed. Sometimes if i give it a little gas it shifts to 3rd at 20mph, I know that's not right. Mechanic said that since my tranny doesn't have the converter lock-up valve in it, the problem could be:

1 - Throttle Valve Cable is stretched
2 - Brake Switch could be bad
3 - Computer could be bad (controls the lock-up)

Adjusting the Throttle Valve Cable helps alot, but doesn't solve the entire problem. Any suggestions, i've been trying to fix this forever.