Hi, I have a 2001 focus, it's a manual and when driving it won't rev past 4k however it will rev up fully in neutral. I've read that it might be blocked cat however it has a de cat pipe so can't be that. I've had this issue around 2 months ago but when I changed the fuel filter it fixed it and surely it can't be the fuel filter again already can it? I'm stuck for ideas and not very clued up mechanically so any help would be amazing!!

Sorry if this is posted in wrong place or already on here I couldn't find it and my first post

sounds like the cars in limp mode its best to get the codes read and start from there

I have a code reader and its not picking up any issues from the car which is what's confusing.

going by what you have said, why not remove the filter, drain it fully, including giving it a good shake, backwards [ie..inlet side} noting the colour of fuel coming out...blocked filter will tend to turn the fuel dirty.

if it comes out clean, refit and test drive straight away see if any improvement....if fuel tank is contaminated in anyway, would soon clog up a new filter

other thoughts...might have a blockage further down the exhaust system,

Yeah if theres no codes it could be a dirty fuel filter theres a restriction somewhere or the code reader isnt picking up the codes still sounds like its in limp mode but there would be a light on the dash to say that