I've had my vehicle for 2 years and done 39000 miles and it has alway had this issue, when accelerating between 2000-3000 rpm it feels like power is on off this on off feeling only last a second or so not noticeable to passengers or rpm, I have changed oil every 7000miles, regular redex, it now has k&n, remapped, blanked egr
Please help

 

Hi mate, are you on about fiesta 1.6 tdci zetec s ?
Because I've noticed the same thing on mine, it's bugging me too,

Car drives fine, just feels like your going on off the acc pedel or as you said,
Funny thing is that my motor only does it in 4th gear at the same rev range you described

I ain't gota clue if you find out
Wack it on here lol

 

It's a focus 1.6tdci but the same engine I've found out its a problem called sticky vane, you can use a product called revive into air intake which costs £60 or use oven cleaner on the hot side of turbo by removing down pipe