I hear that the BG 44K is supposed to be a great product although I haven't tried it yet.
I have been using Lubro Moly Jectron which works for me. The moment I put in in and step on the pedal I feel a difference. I have used this product along with the valve cleaner "Ventil Sauber" in 5 different cars and always felt a difference. The throttle reponse is better and increased mileage. All the cars I have used the products in have had more than 60,000 miles.
Here is a recent thread:
http://www.peachparts.com/shopforum/showthread.php?t=120418