4g63 running issues. runs rough and revs up and down for 30seconds then runs backward

[BradMph]

Just think, if we could reverse our engine running, we could toss out the reverse gear in the transmission,

Do you have a balance shaft also, was a new belt replaced on this too? Make sure the balance shaft was properly set installing that belt. As far as engine running backwards, I think Camoit hit it right with a misalignment with belt or distributor. It's not as complicated as it seems to install a belt and maintain timing, yet it is very easy to get it wrong and set up frustration. Timing light available? Check number 1 piston TDC to number 1 distributor cap plug wire location on compression stroke. Vaccum leaks could be an issue, but as bad as it seems to be, you'd think you could hear the hiss from such a leak.
Belt check would be first, making positive it is correct.
then check dizy position, this can one tooth or 180 degrees off very easily.
Vaccum leaks-only leak that should be happening is the big fat one down the carburetor throat, lol.