Well it depends on the type of car you have. If you have a honda/acura send it to Hondata, they can remap the ECU, or you can just flat out get a new ecu but I think it's like 500 or something, i may be wrong on that. Also, about the compression, if you get really COMPLETE kit, it should come with some better pistons and rods. I got a RSX and my turbo kit is gonna come with better pistons and rods.