Originally Posted by wobbler:
The ST is the original design head and is the closest to the pinto that the Esslinger is based off of.
The XT head has ports raised 1" and larger valves which allows for better flow and more power over the ST.
The RSI head is a mirror design of the XT so that the injection is on the right side of the head instead of low down on the left side where it is more vulnerable to damage.
Thanks Wobbler
