Listen to Pump, the guy, like me, has been around ICD markers for years.
Seriously, I don't like hosed noid markers, which is why Pump and I are bushmaster whores, but the Promaster did suffer from similar issues beyond that.
The regs and valve will give you the most noticeable difference in efficiency and kick. I did have a BKOMaster with an ICDU aftermarket rammer and there was absolutely little recoil.
I would not spend money on an aftermarket bolt....
Hmm, okay deal with the Vlocity....if she works
Marker looks stock mostly.
Go for a valve first and they are harder to come by in the aftermarket world. PM hge2paintball on PBN for a ebay valve.
Some discussion on a new valve he may produce here New Valve Called The Stealth - PbNation
For an HPR, I love AKA regs, but i've had luck with Evil Detonators and they are cheap. Rebuilding is a tad more complicated, but it just requires snap ring pliers and safety glasses if you aren't careful.
LPRs are either AKA SCM-IIIs or a modified micro-rock adapter from vaporworks or zenitram (Airsoldier has these).