I'd try maybe an adjustable piston and a different recoil spring before I had someone messing with the gas port, it's easy to screw up a barrel if you're not careful and most "gunsmiths" are going to try reaming out a larger port with the gas block in place rather than pushing the pins and pressing the GB forward. Which, is just asking for the bit to walk or for them to push all the way though and into the opposite side of the barrel. If it cycles with the can and you open up the port more you're prob going to get a face full of gas with the can on it. Ideally with the adjustable piston you'd have a suppressed and unsuppressed setting and all you'd do is switch the piston between settings.
When you say bulgarian booster, do you mean one of the 4 piece one or the bulgarian copy of the russian cone flash hider/booster? Generally a four piece is going to build more pressure than the cone.
2rivers or POH both do great work but you'll be waiting a bit on both of them since they are very popular. There's a guy on here in NC that seems to do good work and is getting good feed back digitalpaliden I think is his username.
