Hey guys, I've got a Zeal Engineering plug 'n' play megasquirt on the way for my s4 n/a. I'm curious about how much power the other n/a guys have gotten from a good tune. Right now I'm at 172rwhp w/ a mild street port with s4 rotors and manifolds. I'm going to do a real cold air intake (cut up prelude one) with a wideband in addition to this setup. Obviously it's going to be dependent on tuning, but how much power will I get out of the box just from ditching the AFM?

 

I have a completely stock 88 Rx-7 automatic base model daily driver with 120K miles on the engine, that I made up a plug-n-play adapter for an old Wolf 3D V3 stand alone unit, just changing from the stock ecu to the aftermarket ecu with a base map I layed out, I gained 21hp (now around 164 from the 143 rwhp with the stock ecu), and I now average 23+ mpg city...one of these days I'll throw a header on it, and pull the stock air box out then actually dial it in on a dyno...

You have not said what was done to the car other than the ported engine when you pulled the 173hp numbers...so I have to assume stock exhaust and injectors etc, so if you add a header and exhaust system, T2 or GSL-SE injectors and remove the stock airbox (the intake manifold itself is the biggest restriction now), around 225+ is a reasonable expectation for a basically stock street ported engine.
If you want to see some of the more extreme "street ported" engines go to one of the Mazda road racing forums for SCCA E Porduction racers and see what they will admit to...

GORacing