Well, this past weekend I did the plenum repair, and my mechanic buddy went off on me for buying a can of sea foam to put in the intake. I've done the procedure multiple times on my Caprices and I once did it on an S-10 pickup with a stuck valve. That's what sold me on it, that valve broke loose and that truck is still on the road today. Anyway, he told me putting sea foam thru the intake on such a high mileage motor would damage it. In order to placate him, I opted to dump it into the tank instead, but this weekend I'm going to get another can and go thru the booster line. I've yet to hear of anyone damaging a motor with Sea Foam...

Another item of note, is that Sea Foam is not a replacement for worn ignition parts. Initial gains will drop quickly if you have bad plugs/wires/etc.