Originally Posted by KarTek

I think the only things that make a real, immediate difference ar the "direct" applications where the cleaner is injected directly into the injection system. For gassers, I have a 3M injection system cleaner that plumbs right into the fuel rail. For Diesels it's the purge...

The 3M system cost me around $200 and will do nearly every make of car while the Diesel purge setup was basically free.