I must say I am extremely impressed with the GM Top Engine cleaner. It did a really good job on my car, and it seems to be running much better, it revs up higher more quickly, and with less pedal force. In addition, instead of shifting out of first at 6K rpm, it shifts out where it should at 5.7K. The car feels alot more responsive, its running more quietly, and overall I am very happy with it. Anyway, since I personally think that the instructions that you can find here and otherwise are a little lackluster (no offense to anyone whose made a set), I'll run through what I did: First, I made sure I had everything I needed, which I didn't. I needed a 1/2 inch piece of tubing to connect to the brake boost on the intake plenum. All the tubing I had didn't fit snugly/was way too big so I had to go out an buy some tubing. No big deal, plus this gave me a chance to execute step #2, get the car up to operating temperature. Get back and I parked the car on level surface, with the exhaust facing away from my house. I disconnected the brake booster line and connected my new piece of tubing. Realizing the tubing I bought was too big for the can, I fit a smaller piece of tubing inside the diameter of the larger, and then readied the can of top engine cleaner. I started the car up and it revved way up (the large vaccum leak I had created with the tube) and then I stuck it in the can of top engine cleaner right to the bottom. The car almost immediately tired stalling, so I held the throttle at WOT just to keep it running. When I got down to about 1/10 of the cleaner left, I released the throttle, it sucked the last bit in and stalled. Took out the key, cleaned up the tubing, replaced the brake booster hose and waited a good 30 minutes. This initial step created quite a bit of white smoke, but nothing compared to the dense cloud that came out after I restarted the car. The pictures you've probably seen posted of the smoke cloud really don't tell you just how much smoke comes out. I created a fog throughout my entire neighborhood that lasted a good 15-20 minutes (very little wind today) and pissed alot of people off. It was great. Don't be surprised when you try this if you create ALOT, and I mean ALOT of smoke. So, anyhow, after I restarted the car, it was slow to turn over and once I got it running it was idling around 2.5K rpm. I revved it up a few times, and it blew a ton of smoke out the more I revved it. It took a good 2-3 minutes to burn most of the cleaner off and get the idle back down to normal. I was a little freaked when it was idling so high, but I guess its normal as the computer is compensating for the poor "fuel" and trying to make a certain amount of power. Eventually it came back down to normal, and then I took it for a drive. I quickly patrolled the area for cops before making a few passes (hitting 90 in a 30) at WOT to burn whatever was left out of there. By the end of third pass idle was back where it should be and it was running quiet and well with no more visible smoke. Brought the car home and gave it a much needed oil change. The oil smelled like the top engine cleaner (which is pretty rank) and definately needed to be changed. Alot of the crap I'm sure got caught in the Pureone oil filter, but the oil did not look healthy. I let it drain for almost two hours as to get as much oil as possible out of there. Filled it up Castrol GTX High Mileage 10W-30 (I've fallen victim to the petroleum marketing machine, I know...) I would have used my normal 5W-30 but Walmart didn't have it in the High Mileage version so I went with the 10. Also used a new extended-length UPF52 AC Delco Ultraguard Gold oil filter. Started it up and took it for a good 15-20 mile drive. It was running like a champ the whole time, MUCH more responsive and the engine definately was running more smoothly...I'm sure the fresh oil, much better filter, and cleaned motor all contributed to this. The service engine soon light did come on, but after I got back from my drive after the oil change, and started the car up again to move it, it was gone. I got lazy and didn't feel like popping one of the spark plugs, but I'll probably do it tommorrow. I see no reason why they would be in bad shape, I didn't leave the cleaner in there too long (as per the recommendation of many on 60v6.com) so it wouldn't gum up. 30 minutes to an hour should be all it needs. I HIGHLY recommened this to anyone considering it. Just make sure you change your oil afterwards. I think you'll be very impressed with the difference.