Sure, I ... sorta ... understand...but you'll spend a thousands and thousands of euros to supercharge your car, and then spend another few thousand to swap out your 6th gear so you can save a few euro cents on fuel...do you see how incongruent this is?

 

LOL at this logic---> more powerful engine = less fuel consumption when SPEEDING.

Get a 3.3FD as stated, dont S/C your car, or you wont ever make it to work in that unreliable POS, and go get your car tuned really nice. Especially at light throttle cruising. That's how you will see the most gains.