The 1. 5's will give you a little greater increase in the 245hp motor than in other versions. There are several differences in the motor. The injectors are actually smaller than the other motors. The extra power is from higher compression, a different model VP44 & EMC progaming. The actual output in your '01 ETH could be more like 100hp. You will definatly set over boost codes without a boost fooler. If you'r not heavy with your right foot you can get by without other modifications but fuel pressure boost & egt guages are a good idea.