Intresting...im torn, you can turbocharge/supercharge the BMW, but sometimes that causes headaches, then again a BT on the A4 would do the same...

I think i have to show some VAG love and go for the A4. Throw a GT2871R or a 28RS on there, have Revo tune it and your good to go. There is a guy over on Audizine with a B6 Avant running in the 12s with the 28RS setup