here's my setup on my Sig 552:
-DeepFire titanium tooth piston
-Modify aluminum piston head
-Modify aluminum cylinder head
-Sorbo Pad
-Prometheus M100 spring
-Modify air seal nozzle
-Shim kit
-Modify double-groove stainless bushings
-new Hop up rubber & bucking
-Madbull tightbore barrel
-11.1V Lipo battery
OK now, after all that, I know my way around a V3 mechbox pretty good, and I've got a really good performing machine. Nice and quiet, precise, and quick on the ROF. Chronied it a couple weeks ago at the FR game- consistent at 353 FPS. just keep the barrel clean- it can accumulate a bit of crud after a while.
#1 thing with any gun, you've got to shim it, whatever brand it is.
Hope this helps.