Hi, new to this forum but Im sure you can help, I have a focus st170 2003 it's on 98k

The problem I have with it is, between 1000rpm and 3000rpm underload there seems to be like a miss fire. It feels like you have hit a high gear and under 600rpm if you understand?

The engine has had new coik pack plugs leads due/air filters injector cleaners the lot but nothing has changed!

Before I got the car the last owner did say the head has been off because he thought it was a bent valve? But he insured me it was and put head back on pressure test ect. When you do listen to the engine it seems like there is more of a cam knock on the inlet side?

I'm posting a video I hope you can point me in the right direction thanks. As I said more noticeable underload
youtu.be/0lnebyMD-6I