Using GM top engine cleaner
 

I bought the spray kind. Using it on a 98 Z28. What is the procedure to use it in an LS1?

Is the other kind(pour) better?

I've used the spray kind on my car once, but only let it sit for ~3-4 hours. I removed the bellows from the throttle body, and moved the lid/MAF/bellow assembly to the side. I then held the throttle blade open a bit and sprayed it into the bottom of the throttle body. Need to go slow, took about 5 minutes to empty can. I let the idle die when the can emptied and removed the key.

I've heard that it works better if you use the kind which gets sucked into the booster line. I don't recall the specifics on that method, sorry.

you can try a search. theres a lot of other things involved, i think you have to drive around and a lot of black smoke comes out of your pipes. then you're supposed to change your oil right away.
i think...but do a search to be sure.