Unfortunately, modifications do not have a cumulative effect. The highest I've seen a B18C1 with a JRSC dyno at is 230 whp. Good number but you're not going to get much higher than that.

The problem with the JRSC is it's not intercooled. If you try to run a lot of boost the compressor heats up the charge air so much that you loose efficiency beyond about 9 psi. That plus it heat soaks pretty quickly. It's fine for doing a couple 1/4 mile runs but in stop-and-go traffic or on a road course you'll be making much less than the observed 230 whp.