6 speed g/box possible la alex, u will run shorter ratio and for sure u'll shift quicker..using it on gze might be good choice because the better ratio 6 speeder offers..compared to 4agz 5speed ratio (c52 or c56, i dunno which one) with very wide 3rd gear..that's one of the problem a most standard gze can't beat vtec..some cheaper solution, use 4age ae92 ratios (or g/box)..but 6 speed will be a bonus.using 170mm will not lag your performance but increase it.the drawbacks are your clutch magnet will fail quicker, your belting tension will be a problem and your sc unit will become more fragile, breakdown easily.i suggest u go for sc14, just put in all the standard pulleys or slightly bigger,i think 0.8 is still on the safe side for daily driven car, u wont gain very high boost but u gain from the cfm (air volume per minute) pumped by the sc14..u'll gain horses, u'll gain torque, your sc14 running 'almost' standard rotation and last longer and no other reliability problem.been there..it was so much fun..with all the stuffs u got inside ur 4agz rite now..i wonder how much power u can go..180-190 whp? fuiyyo..can already blagak in club4ag already..just my 50cent alex..hehe..we sit in TT la..more we can discuss with all our frens and sifoos here..