Richard Thorne certainly used to remap the S1 and offer other performance upgrades as I recall.
I'm almost certain that 320hp is the figure they quoted. Worth a call.
I spoke to RTCC and they told me they used to take it to a "local" place for the remapping, its not something they do personally and they didn't seem to have any details on power or price as its been a while since they did anything - which didn't inspire confidence if I am honest.
With regards to wanting more power yes around a track better tyres, suspension geometry and driver training will all make more difference in lap times, but on a road none of that really helps as you don't (or shouldn't) be driving to the limit around corners, there should always be a safety buffer.
With regards to acceleration however its fun to use all of it sometimes, and more midrange grunt is always nice. I don't think its worth chasing massive power gains (it is fast enough anyway) but I would like the same level of grunt as the GTN/S2, as I think that is the perfect balance for the chassis.
