Help me wring some power out of my S4

[PzKfW]

Alright guys, I need expert opinion - I have a S4, which is in very good shape, low mileage. I am going to be getting the 6,000mi service soon. At that point, I would like to obtain some more go juice. Here's what I've got so far:

Full Termi spaghetti system
DP ECU
Open airbox / K&N

Bike runs great right now, and I'm 95% happy with the power, so any HP upgrades need to keep the $/hp ratio in the "cost-effective" range. That means, I am not looking for ridiculous expenses, or ridiculous power. Just a nice bump, any easy gains, etc. I sourced a set of spare stripped S4 heads, so I can get work done to them while the bike is still running. I don't want to split the case open to work on the pistons or bottom end.

I did a bit of part checking, and it appears that larger ST4s valves might work (I have a source for a used set, they are 36/30mm vs 33/29 stock). I could also skim 1mm off the base of the heads to get higher effective compression, and maybe add some port work to the heads to boot (I am sure that the intake port will need it if 36mm valves are used). Then, a power commander or other to get the fueling correct. Adjustable cam pulleys to dial the cams.

OK, here's my dilemma: Will the larger valves clear the stock pistons, especially with 1mm off the heads? Will 1mm off the head surface, to raise compression, be doable? If not, are there alternative easy ways to achieve the same thing? Will the larger valves hurt the midrange? If the larger intake valves won't clear the stock pistons, will the larger exhaust valves clear? What about if the heads are milled 1mm? What kind of gains can I expect from valve and port work, if any?

Or should I just dial the cams and be satisfied? (I can always use the spare heads as really neat paperweights)

Thanks in advance.

[jp129]

Have you considered getting a PC3 and a custom tune for your current setup? I find that reflashed maps work ok for normal street riding, but if you're after maximum power gains, a custom tune is the way to go. Plus that route won't set you back much either and can be utilized if you decide to build the engine down the road...

[koko64]

Check out bikeboy.org. Brad has a report on dialling the cams on desmoquattro motors. Got good gains iirc. He may even answer on this thread. Im sure there are other mods he has reports on.
Cheers.

[PzKfW]

That site is a great community resource, it is where I located the cam and valve info for all the different desmoquattro variants. I'd be glad to have his input.