Hi all, I've just had my 1.4 Duratec engined 2006 fiesta serviced with new filters (air, oil, fuel cabin) and oil along with a new timing belt and a waterpump. Since this the car has been feeling sluggish past about 2.5k rpm, and feels like it's running out of 'steam' especially towards 5k rpm where it refuses to rev any further no matter what gear you are in (including neutral).

If anyone has any clue what could be going on it'd be greatly appreciated as other than this the car is nearly in perfect condition and runs pretty well. Thanks!

Coincidences do happen, but I'd be inclined to suspect the recent work and raise it with the garage.   New cambelt fitted a tooth out, perhaps?

If you're 100% certain that all they did was to change filters, then it's hard to imagine what could have gone wrong, other than maybe not putting enough oil back in, which is easy to check.  Replacing the fuel filter may have disturbed some sediment that will block the fuel injectors, which have their own little filters in the top ends.  I can't imagine what might go wrong with an air filter, assuming they actually fitted the correct one and didn't pull any vacuum pipes off while they were at it.  Easy to check.  Fuel injectors can be put in an ultrasonic bath to see what comes out.  You'd be surprised.

Are you certain they didn't do anything else?

19 hours ago, Johnatron said:

along with a new timing belt

The timing is wrong. 🙁

I'm going blind, or mad.  I completely missed the bit about the timing belt.  I think the other posters have given you the answer.