I am going to purchase this gun soon, and I want to upgrade it: http://shop.ehobbyasia.com/ks-p90-tr-airsoft-aeg.html The only thing is, I dont know what the best parts are, or what order to do it in. I plan on doing this DIY mods: Fine Tune Hop-Up Gearbox Air Seal The first thing I wanted to do was Upgrade/Downgrade the spring. I need it to shoot under 315 FPS with .25g, or under 350 FPS with .20g, so a weaker spring(Downgrade) but most likely of better quality(Upgrade). I also want to install an R-Hop. My goals for this build are a high RoF, somewhat decent range(This will be my CQC and field back up gun), and I would like to make it as quiet as possible. I do not know what parts to use, or what other DIY mods to use to achieve these goals, but you only learn by asking questions.... If more info is needed Ill do what I can to supply it... I have no budget.