You can blow your engine with an SAFC. It's a tool, you have to use it properly. Rom tuning just happens to be a much better tool than the SAFC, for less money.

What I'm trying to find now, with much less success, is a cheap datalogger for Nissans. The only dataloggers I've found so far are the standard obd-2 loggers, which aren't really helpful for anybody but s14 ka-t people, and the N-Probe which is freaking expensive at 499. Neat, but really expensive. For DSM's you can get a 40 dollar cable off ebay and use a free logger program to read knock, timing, injector duty cycle, airflow, etc with a 50 dollar palm m100. Couple that with a 50 dollar eprom burner and 20 bucks in chips and a ZIF socket, and you've got cheap tuning. When you're talking 500 dollars just for the logger and 200 for the rom tuning stuff, it makes more sense just to go with a standalone. I'll keep looking for a good cheap logger, but there may not be one until the sr20 thing is a few years old and people start going more DIY with it.