Have Bluespark on my 135 and it is fantastic which a few other tiny mods i have done - i suspect mine has 150 - 160bhp now but its more the torque that is far better - simple to fit and gives a fair amount of extra grunt - on your 165 i suspect it won't give quite as much extra but its cheap (look for the discount code on here on Bluesparks page)
Probably get more with a proper remap but this is reversible and transferable
Works for me