if you're conservative you should be fine running nitrous notirous and turbos are a great combination, as the N2 further cools the charge. in an N/A engine, it's a big riskier given the higher compression, but in somehting like the skylines of japan, the low compression allows for easy F/I, and also Nitrous. many WRX owners are running larger IHI turbos and wet kits with fantasic results, while also claiming that it is very safe. no adverse A/F numbers, EGT's are staying low, etc.

the limitations is the same for both options. the more boost, the less of a shot you can run.(and visa versa) becasue they are the same effective mod, (cooled, compressed intake charge) the engine still has a fixed limit for boost. both aproach the limit in a similar manner.

dR