Foam as in head? Or the beers not carbed after several weeks?
If its the latter:
There tons of pour methods to create a larger head.
Pour right in the center of the glass before tilting and cascading down the side
You can also just crack the tap open and let the smaller output release the co2 out of suspension when you right at the brim.
IMO longer lines need higher pressures to get the "american pour",
Go to england they serve a TRUE pint with no head AND at 50-55*!
I tend to overcarb (on styles i want high carb) and then back off the pressure so the change from keg pressure to atmospheric pressure is much lower resulting in a perfect "american pour" yet still full of carb in the body.
Good advice as always. When I get a chance I will start trimming it down. What should I look for as an indicator that I've found the "sweet" spot?
ID say when YOU think its right...Remember warm line will pull co2 out of suspension faster than a cold one will, trim and wait an hour before pouring.
Also an FYI, might just be on my system but the first pour of the day always tends to be a lil foamy,
Solution? Pop the tap to dispense the spent beer in line (10ft should yield 3oz) and you should be good to go. the 1.5oz(have 6ft lines) is petty to me and much better than screwing with lengths and pressures day in and out!
Cheers!