Im using Valet Pro PH Neutral snow foam, 1 bottle has lasted me well over a year,..
http://www.cleanyourcar.co.uk/washin.../prod_500.html,
2 or 3 pumps and 1 cap full of megs NXT car wash mixed in the bottom with the rest hot water.. and it foams very nicely, lance turned down by 3/4 of a turn from fully rich, it also won't strip any wax or sealants off.
If you want it really foamy then run the hot tap into your pressure washer
im assuming your using a decent lance.