I'm on my third E92 M3, and I've gone through lots of modifications over the years I've owned the cars. When I ordered my newest M3 from Germany several months ago my goals for modifications were to create the ideal set of changes with minimal cost. I visited Sal at Evolve when I lived in the UK last year and asked him what the restriction points were on the car. He told me that the primary cats were a big issue, their design is far too restrictive and cause up to 2 bar of backpressure. The rest is simply tailoring how you want the exhaust to sound, until you're talking forced induction.
Bearing this in mind, my solution was to install Turner's test pipes (thanks go out to Alekshop for getting them installed in time for the race) in place of the primaries, have Evolve tune the car (which also has a Dinan intake I've had for ages) and then do the alignment pin mod with an aggressive alignment & -1.5 deg camber up front. Evolve surprised me with a Servo modification included in the tune file they sent which, combined with the alignment, felt absolutely perfect.
My first US car had Dinan stuff on it, the Stage 3 suspension, intake/ECU/slip-on which I ran for a few years at a timed hillclimb race I've been doing for the past 8 years. The Dinan suspension feels awesome to drive on, but it's too stiff, especially for California's crappy roads in the Bay Area, so I decided to try out the stock setup with the pin mod and see how it went.
I posted videos here:
http://www.m3post.com/forums/showthread.php?p=14684301
The result is that this car, with these modifications, was a full
12 seconds faster on this course, beating an E60 M5 and several other seriously quick cars. A 4 minute run is a good time for a fast car & experienced driver. I'll hopefully get some dyno sheets soon, I'm thinking about flashing it to stock then back to the Evolve tune to see the difference. The butt dyno definitely feels a difference, and it's hard to argue with the results of the race.
Since I'm a returning Evolve customer with the same car, they did the tune for just the cost of the programmer, so $200 + $400 for the pipes and $250 for installation put me at $850 total. Not a bad outlay for a great result.