If so how much is a map like this roughly and are you likely to lose much hp??

 

You can map on whatever UL you like. But the lower octane stuff doesn't resist the onset of detonation as well, so boost and/or timing has to be tempered - and/or fueling increased - so as to to be able to map it safely/responsibly.

As a corollary, you won't make as much power as 97-99 (everything else being equal).

 

On my05sti.ppp had it remapped to run 99 ron. Bhp 340 but mpg was improved loads (can you not get 99 ron)and much more drivable .

Is your's new age or classic?

Mark