No more flat spot
 

Well my 02 curvy had a very nasty flat spot around 5K revs.

Cruising at 50ish for awhile and then trottling on what a noticable and annoying flat spot. Has anyone ever noticed one. Mines got 26K miles.

Anyway, put two tanks of super unleaded and after that it's gone and I'm almost finished with the tank of cheap (er) stuff and the flat spot is gone. For a couple quid more per tank it's worth it.

Re: No more flat spot
 

You're probably just a touch lean on the main jets, that tends to be most obvious towards the top of the midrange as they starve the needles a wee bit. Though to be fair, I wouldn't have thought super unleaded would make any difference to that.

Re: No more flat spot
 

I wouldn't have thought so either but someone suggested it to me and it worked. I don't thinks it's typically too lean because this has progressively got worse over time so I think it must have just been getting gummed up.

Re: No more flat spot
 

Certainly decent fuel additives clean the engine (inlet valves are the biggy), though Optimax etc. are sometimes more dense so you may have richened it up a little from that. The flat spot is worst around that point though, most likely down to noise checks or summat, if oyu get any dyno fiddling done it goes away