ok mate .. -31 is a progresive actuater and gives a nice smooth power curve and starts at around 5 to 7 psi now the amal valve takes up alot of slack from the actuater spring so you dont have to wind the actuater up much.
but if you had no amal and used a -31 you would have to wind the actuater spring up loads and the spring wouldent last long
ok part 2.. -34 starts at 14 psi and comes in with a big bang so has a very strong spring so you dont need much wind on the actuater..my s2 spikes at 17 and holds about 14 psi with - 34 and no amal
sorry its abit complicated but thats whats this forums all about .. learning


andy