Beg to differ massively!!! It worked a treat on an old Xr2i 16v, and a Honda Prelude V Tech and now my V6 Mondy. Obviously the more in need of a clean your engine is, the better the performance re-gain.
I used the cataclean stuff in my old mk1 v6 a couple of years ago, the emissions went from barely passing the mot to barely registering on the analiser machine. Absolutely gobsmaked i was, haven't used it since, bit wary as it must be some potent stuff.
I used 10k on my 97 TD and what a difference, MPG went nearly 48mpg with a heavy right foot :whistling: and general running was alot better! When you spray it in the white smoke that comes out of your exhaust makes you think you've broke the engine :L