I don't know much about the banks, but I saw a deal about the throttle body spacer....I asked on here what people thought if it would really work, and most everyone I talked to said it didn't do anything since the air was fed into the turbo the spacer wouldn't really do much. Maybe if you search the threads you'll find one about it. You can make your own intake, there are alot of write ups on how to do it, and it work pretty good and is only $50-75.
This should be link
DIY Intake
There's also a mod to turn your EBPV into an exhaust brake, that would help on the downhills. I'm sure there will be others along that can explain it much better than I can.