Start on the valve end first.... leave the bolt for now.
As 3022 stated the valve in that gun was designed to run off powerlets (liquid co2) you are now feeding it with Constant Air (gas) so you need to open up the ports in the valve.
You can either send this out to have the work done or do it yourself. This is not the easiest task, it can be a little tricky and by no means will you have a Palmer tweaked valve if you do it yourself.. they have it down to a science... on our 10 job we'd still be considered hacks.... but you can do the work.
The opening of the port between the tubes requires even more skill.
If you find after opening the ports on the valve, and using the correct springs (order the springs from Palmers for constant air guns.. they are pretty much the same though) that you still have the need for more work.. I would go with a one piece bolt from palmers.
I've never had blow back or blow by issues with my speed-demon bolts and I dread taking one apart just because they are a major pia to put back together. First try lubing the bolt with grease/vasoline (lube the inside of the bolt the expanding portion/slider not he outside) and you may see some of your "problem" disapear.
But start with the valve... that is where you will get your greatest improvement.