Get the ML crazy jet inner barrel. Just upgraded to it over the weekend and its way better than the angel custom one I had. Still using a stock spring guide (with an M150 spring) and it's not a big deal. Might upgrade to a steel one soon. I use the same AA 90 Z-trigger with an AA 90 degree piston/ML 70 bucking/AA hop-up and it works great.
Don't know what else you can really upgrade besides maybe the cylinder head? Also do you have any barrel spacers?
Don't know what else you can really upgrade besides maybe the cylinder head? Also do you have any barrel spacers?