Possible Tranny slippage

I just changed my transmission fluid in my M, and I used Mopar ATF +4. It also recommended that I add a bottle of Lube Guard (purchased from Napa). Since I've changed the fluid, it's much harder to smoke the tires. Seems like it's slipping! Anyone have any experience on this topic

How many miles on the trans? make sure the fluid level is correct. Too much or too little will cripple the trans...

The tranny has 121,000 miles on it. The fluid level is perfect. I've changed the fluid 3 times since removing the tranny additive. Everything seems perfect now. I'll never add anything to this tranny again. Only Mopar ATF +4 will be added from now on.