Not as much as a traditional springer, but something is possible..
On my 90 (.25) I've replaced the factory seal with a Venom Power pulse, polished the piston outside diameter, reamed the transfer port size from 3mm to 4mm.
With the small tp the rifle was prone to burn the factory seal with minimum variation on ram pressure (factory spec press. is 24-25 Bar); using the Venom seal in conjunction with the enlarged tp, I pressurized the ram up to 28-29 bar with no problem (22FP at this press.). Anyway found best performance around 20-21FP/27Bar. Venon seal gives far better firing cycle too, but you have to start with an oversized one and turn it down to the best (tight) fitting on the tube...
Noticed that GR prefers a bit larger TP size than the similar size traditional springers.

Roberto



<BLOCKQUOTE class="ip-ubbcode-quote"><font size="-1">quote:</font><HR>Originally posted by ianb:
Basically can you, I know you can venomize certain spring rifles, but with the sealed internals of a gas ram is there any scope for tuning, improving.

cheers Ian[/quote]