There are many mods for the Marauder. I have the rifle, not the pistol, but in the search for more shots, I too made many modifications. Finally, what worked for me?
To start, I have a .22. I tried every standard adjustment in the book. Always maxed out at about 30 shots per fill no matter what I did. After extensive conversations online, I purchased a regulator, new lighter hammer (kept old striker) lighter spring, and new transfer port. After many hours of tinkering, tuned it to about 850 fps with the JSB 18 grain pellet. Now, 50 shots per fill (actually more like 60 before it falls off the reg, but I like a little cushion),
I believe I purchased the parts from Tim Hill of Hill Airguns. Tim and Tom Holland were great helps. But beware, the journey took several months and you need your own compressor. Only way to adjust the reg is to degass, remove and adjust the reg, put it all back together, air up, shoot, and do it again.
I wish you luck in your quest, It can be done, I've never done it with the PRod, but should be similar to the rifle.
Enjoy!