Tranny/shifting issue

[stryker6040]

Using my 87 custom performance tune it seems my truck too has the gear lock up problem. it cant seem to make up its mind between 3rd and 4th between 50mph and 60mph on flat road with no load. it will go to 4th but wont lock then all of a sudden it will back down to 3rd and lock for a second before it think it should be back in 4th but doesnt lock there either.

Also having an rpm issue while driving on highway with CC and AC on which wasnt there before on the canned gryphon. RPMs seem to surge for about 1-3 seconds every mile or so. It feels really weird cause out of no where the truck will just start to pull for no reason and the exhuast will get louder, and then goes away. With the AC off there doesnt seem to be an issue.