Originally Posted by Hambletonian

My car is Naturally Aspirated, but acted similarly to yours. Sluggish throughout the drive train. Turns out that the left-rear speed sensor was bad, causing the car to do peculiar things though activating the electronic speed controller. A fairly simple sub-100 Euro fix.

Good luck. Hopefully it's not in your supercharger inter cooler. Yikes.

PS: Have you ever reset the throttle control memory? Makes a remarkable difference.