is this better or as same as power FC?
does it work on auto?
It basically accomplishes the same thing as the PowerFC. The two differ mainly in that the PowerFC is a much more expensive standalone unit that completely replaces your stock ecu, whereas the GReddy e-manage is a piggyback which makes adjustments to what your stock ecu does. With the PowerFC you can do a few more things like play with lift engagement on the GTS and make adjustments to the Intake
valve timing, but that's really dangerous to mess with unless you really know what you are doing. Since the GReddy e-manage is a piggyback and allows OBD-II codes to still be run off the stock ecu, you can possibly pass smog with the e-manage whereas all your tuning on the PowerFC (non OBD-II) would be for nothing at smog time, and you would have to pull out the PowerFC and put the stock ecu back in for the test, but then you may subsequently run lean causing check engine lights or trouble codes and probably won't pass smog at that point (unless you pray hard enough and it's a miracle). So in conclusion, if you don't mind the price tag, the potential hassle of the PowerFC, and especially if you have a GTS and a 2002 at that, I would go with the PowerFC. But if you are more of an amateur racer and not looking to go pro, then I would stick with the e-manage so you don't have to reconfigure and put your car completely back to stock every two years to pass smog (after the initial 4 yrs CA). The fuel map is where most of the gains are made by making sure your engine is getting just the right balance of air/fuel, and the GReddy e-manage handles that task beautifully.
Personally, I bought the e-manage thinking it would be a lot more convenient smog time, but then I decided to do whatever it takes for ultimate Performance since I may actually go pro in all-motor NHRA (at least try) so I just bought a PowerFC, which hasn't arrived yet. Plus it makes economic sense b/c I have the 2002 GTS ecu which we all know as the low rev limit of 7800 rpm instead of 8400 rpm so I would have to spend money on top of my e-manage getting a 2001 GTS ecu. If you don't have the '02 GTS ecu and you're not extremely hardcore about racing, and you are worried about having a car that might not pass smog, you'll be happy with the GReddy e-manage.
C2Gas, owner of C2Power and maker of great Turbos uses the e-manage simply because it works well with Turbos and if you are possibly thinking of going that route later on, and want to keep your car smog legal...then that's pretty much the only way to go, barring having to completely remove your Turbo kit just for your smog test (if you had the PowerFC). Also another big downside to the PowerFC is that you have to know what you are doing when it comes to auto mechanics because if something is wrong other than your knock level, your car will NOT tell you since it is not OBD-II compatible. That is you won't get any check engine lights and you could have a major or minor problem with any of the systems in your car. With the GReddy e-manage you will still get check engine lights if warranted and still be able to read codes with a scanner. So it's not just an immediate decision about saving $1000 with the e-manage..it's about time and convenience which is also money.