4th gen 3sgte differences are compression, turbo, and boost. The 4th gen has some sort of new age ct turbo with the turbine housing casted into the manifold, they have raised compression and boost as well. and thats it. nemesis is a good unit, however 1450 shipped without wideband, without two step, etc... it can be put in there with an extra cost. if you need to have a plug N play system i would go withthis for ease of installation and tuning. Howver if you want a balls to the wall stand alone and you don't mind learning and spending some extra cash... aem all the way. Or if you want a good system (better yet great system) for less money and you don't mind following directions (ie solder pin 16 to red/blue wire). Perfect power ecu is great as well as the microtech both can be had for under 1000 and has many features.