I have a 99 Cavalier 2.4 and the other day I was driving and I noticed the car felt like it had no power. I could hold it to the floor and it'd get to about 4000 RPM and it felt like the transmission just started slipping. I decided I'd try some of that Lucas Oil Stop Slip stuff. I put in the amount it said to and then started to drive the car and I noticed the ETS off light was on and now the car acting even worse. It won't shift out of first gear and won't go above 3000 RPM but now it doesn't feel like the transmission is slipping its almost like I'm hitting a rev limiter when I get to 3000 RPM. Any ideas?

Do you have any engine lights on of so pull the code might be bad transmission valve solenoid. But with limited info no way to tell you what it for sure.