For a stock, unregulated marauder, I would port the valve exit and barrel port to .157", and then I'd use either poly tube or make my own transfer port from acetal/delrin which cost around 5-6$ for a 6-12" piece, alternatively Ace Hardware sells Nylon tubing that suffices at just .20-.40 cents...
That alone should bring the power up and would be tunable for 3,000 psi to 2,150 for 50-52 fpe for a good bell curve. Very budget friendly build that can cost less than 10$.....toss in a SSG, light weight valve spring, MDS hammer, custom delrin poppet @ .275"~ OD with a stem thinned @ the area it occupies the valve throat down to .09", mild bolt probe modification (thinned and pull back shoulder slightly) and for under 100$ you can port to .187" and easily make 60 FPE (900~ fps with 33.95 gr) with the marauder on the same 3,000 to 2,150 fill range.
The above valve would open easier than stock due to less pressure differential across the poppet and ATM thanks to the reduced OD, and you don't have to drill the valve throat or risk damaging the valve seat thanks to the slight thinning of the valve stem where it occupies the valves throat, which again reduces the force required to open the valve compared to a valve that opens the valve throat to accommodate the bigger .187" ports opposed to the thinned valve stem.
-Matt