they also kill your fuel allowance for the week also, but hey to some thats not much of a concern. Friends fuel went up about $20 a week after he lifted the converter speed from 2800rpm, to 3500rpm. Mind you this was in a carby fed 304 V8 with 275kw on tap, cam didnt start to rumble until 3300rpm, and then the car launched like all buggery, its now a 355 stroker (not his anymore tho)
anyhow back on track, i doubt your I6 will require a higher converter than the stock one, if your going to drag your car every week then sure get it, otherwise put that extra dosh into getting a Dev4 kit instead.
plus the dev kits improve power down low also, its not like the cam or turbo (in other cases) is only starting to build up at 2500rpm. One good thing tho is you can rip it up whilst driving along, as it will stall up more, to a better power region, and then grip and say hello to wheel spin galour. Thats only if your car has plenty of power. Doing that on the road is bad m'kay...