EEC Tuner is cheaper than a Tweecer and does the same exact thing.
I'd HIGHLY recommend that anyone buying a chip either buy the EEC Tuner or a Tweecer.
The only thing stock on my engine is probably the Brackets for the accessories.
The EEC Tuner allowed me to remap my MAF meter settings to match my engine, allowed me to change the fuel curve, again to match my engine, allowed me to cure the hot start issue with having larger injectors on the car, and allowed me to adjust the spark curve inconjuction with my boost. I can change the rev limiters, how much timing my car has, how much fuel it can have, how long injectors pulse, how to interpret the 02 Sensors (Especially if you have long tube headers), tell the computer I have no EGR, No Smog pump, etc. (You can do all these things with a tweecer also.)
I just dont like chips that you plug in and have no ability to adjust them.