The way inline blowbacks work there is nothing you can do to increase accuracy by upgrading the internals. What you can do is invest in regulation switching to HPA or making the most of CO2 will get you shots that are on target nearly every time and buying better paint or maybe even buying a barrel kit will also help a lot. I know you probably want to hear that there are shelves full of flashy upgrades you can buy but better paint and a simple regulator are really all you need. Not very sexy I know but there you have it.
