If the Amsoil ATF is working good for you I would stay with that, I found in my case I have better shift feel with an MTF. It seems the higher up I go in Viscosity the shifting feels better to a point.
ATF+4 is about 7.5 cst@100 and felt very notchy, Amsoil ATF is 7.6 and was better, then I tried Redline MTF which is 10.6 and it was fine once the fluid warmed up, but cold shifting was terrible. I then went to RP Snychromax MTF which is 7.7 and I am pretty pleased with it, but I am going to try the Pennzoil/GM Synchromesh which is 9.0 and see how that works out.