Max is right. It can make a big difference. Have you tried running it without any juice to see if it runs like it used to? Also has the car slowed down? If it hasn't slowed down it doesn't sound like anythings slipping. Any slippage will slow a car fast. Especially if you have allot of horsepower.
I havent ran it without the juice. I did notice the light was coming on earlier and earlier in consecutive runs. So something is slipping I would say. It would run the 1/8th about half way through 3rd gear, now its on the limiter..