I was successful at loading a non carb canned tune with a used $350 Hondata tuner-was worried it wasn't working, but it does.-a bit of a battle to figure out how to get it to work-used the hondata web site to get the software. changed redline to 7500 and got rid of the rev shifter lag, also got rid of the speed limiter of 136mph, now it might be able to do up to 168mph at 7500. I recently got a new smart phone that I can use with the blue tooth function on the Hondata tuner to monitor the honda si engine in real time which is quite important. a/f, coolant temp. I don't know yet all the things it can do. There is a canned tune for 3.5 intake and one with a 3.5 intake and 3" exhaust without a cat. I would run a free flowing cat so it can pass inspection, I hope. The 2013 si has a very restrictive exhaust, the biggest gain would come from a free flowing 3" exhaust. It's like honda was nurturing the car with its crappy tune, shifter rev hang, really low speed limiter and exhaust. Anyone who drives a honda si can tell this engine is special the way it wants to rev higher than most cars. I am still learning on how to drive it. It seems to really like revving up the engine quite high, it does not like low revs. Still looking for a tuner. The weather is nasty and salt on the road so I am barely driving it till spring time.

This is a very high tech car and a tuner should all ways be the first thing you do.