Yes, a FPR is needed with a 255. Its not at higher rpms that its lacking in, its the lower ones... the stock FPR is geometrically not big enough to get rid of the excess fuel fast enough. Aeromotive makes a good one, IIRC they are around $300 with the install kit. They arent overly difficult to put in, but they do need to be mounted to the firewall. Yes, you will need a tuning device. On the 650's you can get a SAFC variant, but then you should also have a pocketlogger to do some data collection. By the time you've coughed up dough for those two things, you might as well get DSMlink... its a far superior tuning tool and data collection device and its priced pretty decently too, about $550. You wont need an external gate, but porting would be nice. The 16g variants like to boost creep past like 5000ish rpms and some decent porting can help out with that.