Are you looking to just shift 100% of your racing to tarmac, then? If you had the D2 valved and tuned for gravel (rallyx), they might not perform as well on tarmac. I'm going to assume you've gotten out more than a few times already and want to make the car faster, but if you're looking to turn your back on rallyx, you might find adjusting your valving and spring rates (and maybe dialing in your brake balance) will help you attack the corners better, carrying more speed through the corners.
Of course, if you would still like to do the odd rallyx from time to time and are willing to compromise absolute tarmac performance in order to preserve the car's ability to get dirty and sideways, then maybe you DO want to set your sights on the engine. First thing I'd do is strap it on a dyno and have a look at the torque curve.
A rallyista once told me, "When you can turn entire laps without lifting, that's when it's time for more power." How often do you find yourself flat out and need longer legs? I'm only asking because I hate seeing people spend thousands again more before they truly tune the most important part of the race car - the driver. /ubbthreads/images/graemlins/smile.gif
Have you considered playing with intercooler/piping size? What about exhaust? I suspect you could do a lot of very interesting stuff just by playing with intake and exhaust piping. What if you had a 3" downpipe step down to 2.5" after the cat? What happens to your torque curve if you run 2.5" from the compressor outlet through the IC, but stepped back down to 2.0" after the BOV flange? See what I'm saying?
If your idea of racing demands more than peaky power and keeping the car straight for a few seconds at a time, you want torque and you want as much of it on tap across the tach as possible to pull yourself out of the corners. I think 272s would shift the powerband higher and cost you low- to mid-range torque. Finely tuned strut valving and spring rates, and dialed-in brakes, combined with a nice, fat torque curve should allow you to brake later, carry more speed through the apex, and pull away from the competition better.
My .o2.
