Bruce,
Gaining actual numbers is not as relevant as gaining percentage. A 500E probably varies 30HP between optimal and poor conditions/temperatures. That is less than a 10% difference on that motor. On your 185HP motor picking up 30HP is about a 16% bump. I'm not saying its impossible by any means, but with less HP (and of course less weight to haul around) little gains can make a bigger difference.

Benzmac...just a thought, back me up on this IF I'm on the right track. If you use the old hot rodders trick of adding more boost (kompressor pulley size swap) the computer will take timing out to compensate, correct? How hard would it be to change, recalibrate, or outright lie to the MAF sensors? Seems that a pulley change for more boost, the sensor mods to keep it working, and some computer tweaks to make the most of the changes would be the most logical way to get real gains off the motor. Messing around with exhaust and K&N's might get you 5HP total if your lucky... Assuming the motor can take more boost without knocking you should be able to get near the 200-220HP neighborhood.

Renntech makes some tweaks for the SLK but you could buy a new SL500 for the what they will charge you. Of course, you could just wait for the upcoming SLK with the supercharged V6 that is supposed to be a M Roadster/Boxster S fighter...

Just some thoughts...Lee