Get the Female Stabilizer kit for the 98 series. Make sure you get the correct one as the Platinum series uses an inverted flare fitting for the gas line connections. All other 98's use a 1/8 NPT connection. I would also look into getting a rear velocity adjuster.
The way I would set the velocity is as follows:
- Back FVA all the way out so it is flush with the inside of the power tube.
- Screw RVA all the way in
- Screw in full tank.
- Adjust reg pressure until you are shooting around 300 FPS.
- Adjust RVA until you are shooting at or 5 FPS below field speed limit. (If limit is 285 set for 280) Personally I keep my 98's shooting around 275 FPS.
- Play paintball
Also make sure you are using good paint as you will have better shot to shot consistency. You can have a well tuned marker but if you shoot bad paint you might as well shoot a rental that hasn't been serviced for the last ten years.
Another thing to look into is getting an HPA tank. If fills are readily available where you normally play it is a better option. The output is already regulated between 750 PSI and 850 PSI on most high output regs. Some manufacturers have a different output than others. The regs for a 3,000 PSI (3k) PMI (Pure Energy) tank output around 750 PSI while the old Crossfire 3k regs output around 800 PSI. The Crossfire Stealth System regs output around 850 PSI. If HPA is a viable option for you, all you need is an RVA
The main drawback of HPA is the cost of the tank. You are looking at spending over $100 for a brand new fiber wrapped tank. You can find them cheaper used, but you need to check to see if the hydro test is up to date. Most are good for five years from the last date it was tested. Unless it is a good deal I would pass on anything tested in 2009 or prior. You also want to watch the age of the tank. The fiber wrapped tanks we use in paintball are only good for 15 years. I would stay away from anything made in 2000 or earlier.