Various Nightmares! Mk2 1.6ti

Hello you knowledgable bunch,

As with anything car related you put a search into google and it offers results and they’re usually loosely based on what you’re after so thought I’d give the forum a go.

Had some issues with my 06 Focus 1.6ti, firstly needed to have the coil pack, leads and plugs changed. Then replaced the coolant expansion tank, the replacement didn’t have the best fitting lid and I’ve been continually losing coolant, a further replacement has been purchased. But more recently I’ve been getting a juddering, almost hesitation under acceleration. It’s only between about 2500-3500rpm and if I put the car into a gear that’s too high for the speed and put my foot down, whilst the car eventually gets upto a speed ideal for the gear I’m in, I get some popping and banging from under my feet that happens with the juddering. Having a decat exhaust in the past it sounds like a toned down version of exhaust pops but they aren’t coming from the back box but from under the car around my feet. 
 

I’m completely fed up with this car and having to fix things on it, if anyone knows roughly what I’m dealing with and whether or not it’s an easy fix/cheap fix I’d love to hear from you.. If not does anyone know of a decent cliff I can push the car off! 
 

Thanks in advance.