Its funny this should pop up now, the same week that I am working on a 3 stage performance enhancement package for the 2.5 Boxster engine.
Last week I was able to take power output of one of test cars (2.5 with 38,000 miles that we have not modified internally) from 164 HP to 192 on our Dyno Jet chassis dyno by applying several bolt on procedures including de-snorkel, K&N replacement filter, a set of our most recently developed headers and muffler and then topped all of this off with an under drive pulley.
With the first stage development applied I am getting better MPG and the car runs better and is much more crisp and throttle responsive. The torque is increased throughout the RPM range and due to that drive-ability is also enhanced and even my Wife like to drive the car better now. All around the engine is better and it's certainly not just on paper as the acceleration is now through the roof!
This week I am working on the second stage of the kit that will include some other bolt on induction changes and believe that after these are done and we develop an ECU flash for them that 200 RWHP is a possibility with this second stage of the package.
In my experience the stock 2.5 cars have adequate brakes and suspensions for up to a 75HP upgrade in performance, and the cars really wake up around 200 RWHP, and are fun to drive. (actually being able to throttle steer them is fun!)
Historically, the problem with enhancements for the M96 has been that no one knows what is compatible and performance packages that are proven have not been available.
You can read more about the test work and keep up to date with the developments on my forums, here
http://forums.aircooledtechnology.com/showthread.php?goto=newpost&t=3138
I'll be posting graphs and data on my forums in the coming days and even some video of the car before and after the changes with the data mixed in as a heads up dsplay for comparison. The data logger is now in the car for field testing.
As for other enhancements like Turbos and Superchargers:
They make real big power, but the engine already has reliability issues and these "power adders" are catalysts for failure for a stock, non internally upgraded engine...
If you want big power, turn the 2.5 into our Big Bore 2.9 and see 250 RWHP for the same cost as a stock factory replacement engine.. Heck we can build that 2.9 into a low compression engine with forced induction cams and heads and then big power over 350 ponies is a possibility as a bolt in with no conversion complications.