I found the throttle response on my 03 FE650 Dellorto absolutely fabulous, no flat spots to tune out as has occurred with every FCR equipped bike I've touched - the problem is it didn't have the grunt I expected. Just to add to the diiscussion, here's what I found best for the 03FE650 (dellorto), 04 FE550 and KTM 520 I've owned based on dyno results and riding
650 - 33Pilot, K51 Clip 2.5 or 3, DR 270 185 Main, 40 mm Dellorto (48 hp) - disappointed as I traded the KTM for this and it's defficiencies were immediately obvious
550 - 38 Pilot, 75 PAJ, 158 Main, 200 MAJ, EKP 4.5, 41mm FCR 2 (55 hp) - thought I'd give Husaberg another go based on the 04 improvements, well worth it
520 - 48 Pilot, 100 PAJ, 160 Main, 200 MAJ, EKN 2.5, 39mm FCR (53.5 hp) - a great bike, however the 550 is better.
All bikes similar (straight thru pipes, same Dyno, same time on the dyno, same rider, similar density altitude).
Taff, I tried no MAJ to lean the top end on the 550!