Did I read correctly that you don't rev past 2,000 rpm? Peak power is made at 2,600 rpm for most variants of this engine (not sure which version of the B3.3T you have) and governor break speed is up around 2,750 rpm on some of them. May want to rev it out more to get some much needed power from it, because you're likely making <65 hp at 2,000 rpm.
Regarding the question on the intercooler; Cummins bumps the torque output by quite a bit on the intercooled B3.3TAA. It jumps from 181 ft-lb @ 1600 rpm to 224 ft-lb @ 1600 rpm (again, this is engine configuration specific). This may really help get your cruiser up the hills!
Great little Japanese engine, but it's got it's work cut out for it pulling a Cruiser up and over hills. This engine is typically used in fork lifts and smallish skid steers! Not talking down on your choice or build, and frankly I'm envious.
Dan