[ReSpEcT]

From my understanding you can upgrade your gun to 400FPS without changing the motor, so you can keep your current TM motor. I believe stock TM's shoot at around 280FPS.

You would need a new battery, if your current battery is a MINI type and probably stored in the handguard then you will need to purchase a battery pack with C type cells (larger) in order to supply the amount of current being requested from your motor. The motor will draw more current in order to pull back the stronger spring, that is why a larger battery pack is required. The C cell type battery pack will be too large to house in the handguard so you can either house it externally or re-wire the mechbox to the rear of the gun and place it in the stock.

Once you have purchased the new battery then you can try upgrading the mechbox internals (gears, spring, bushing, piston, etc.).

There are other ways to improve your FPS without modifying your mechbox. You can try upgrading your inner barrel to a tighter one (6.04mm) which may increase FPS by about 0-10. Also try adjusting your hopup, to make your BB's travel farther. These upgrades do not guarantee an FPS boost as every gun will have different results. Good luck and read some stickies. Just be cautious of the increased rate of wear on the gun, like the shell of mechbox, motor, etc.