I know you can re-pin a 730 to work with boost. If this is true, what IS the physical difference between a 730 and 749? And if I'll be going from a 165 to a boosted 3-bar MAP application, which ECM do I go with?

 

I think the main difference is that the 749 has an extra injector driver giving you more options when choosing what types of injectors you want to run (low vs high impedence). Aside from that, they also come with different map sensors (1 bar for the 730, 2 bar for the 749). As for the 3 bar map sensor, it should work with both the 730 and the 749. But the thing about the 3 bar map, when tuning with the $58 code, you have less resolution than you do with the 2 bar map. This could make it harder to get the perfect tune. But I dont have any experience as I still have the 2 bar map sensor in my 749 (and currently its sitting on my work bench, 730 still in the car), so be sure to verify with other 749 supports on the boards.