If I had it my way, I'd have a small centrifugal supercharger running at about 6psi, an air to air intercooler, open up the intake a little, a nice stainless header and a mild stainless exhaust that's just about as quiet as stock. I hate noisy exhaust systems, especially on a 4-banger.
All four of those mods combined would be good for a real world 70hp and torque (190hp and 200ft lbs or thereabouts), which means somewhere in the neighborhood of 160-170hp to the ground. I'd be happy with that and would easily shock the hell out of a lot more people! ;D
And just as a side note, I've found that 3rd gear is where this little thing really pulls hard and will hang with a lot of vehicles under WOT. I still hate that damn hesitation of the drive-by-wire crap during fast shift changes. I'm trying to compensate with the throttle, but still feel it. I want a real throttle cable again darn it!!!!!