iv got a few mods on mine and will list my opinions on each one.
underdrive pulley freed up some "wheel bhp" and i felt a difference.not mega but an improvement. k and n induction.no differnce. ss exhaust no difference. dreamscience handset on cais 97 map. this again was noticably better but again not mega. exhaust vernier is latest mod set at -6 and i rate this one.a noticable difference that put a smile on my face. on their own they dont mean much but for me if i add up the underdrive pulley, dreamscience and vernier the difference is a fair improvment over standard but can prove costly unless you get them all second hand off ebay like i did.

i have a 5.4kg ttv solid flywheel ready to fit and this is supposed to be the biggy so cant wait to get this on but wont be for a little while