The difference between the Kev mod and the PC becomes apparent when you start tuning your fuelling using a dyno. The ability to build a custom map allows you infinite control over your mixtures and ratios. The trade up is how much do you want to spend to gain a bit of extra torque and some hp. I run a PC but to my mind the Kev mod is amazing value for money! Also consider doing the O2 mod because that makes a huge difference to a/f ratio which is what causes hunting at low revs. This site had some very good PC maps as a starting point if you don't have access to a dyno.