The GReddy kit for the GSR isn't really that small. In fact if you get the intercooled kit you don't have to do any less work than if you bolted on a Drag or RevHard kit (as in, just install what comes in the box).

The JRSC runs less boost so you can get away with just running an FMU and MAP check valve and be fine. But to get any sort of boost setup to be truly RELIABLE you'll actually have to tune. Ain't no way around it, sorry.