Ford Focus 52 plate 1.6 cutting out

Hi!

Problem with my 52 plate 1.6 ford focus elle. She loses power and eventually cuts out when on low revs/ in low gear, usually when engine is warm, after about 60-70 miles. When I try and drive when she loses power, the accelerator doesn't affect the engine at all. It just revs and eventually cuts out. Sometimes I can keep her going but with no power, and hear an awful misfiring sound from the underside (exhaust manifold area)
It feels almost like fuel starvation (it's not the pump however, I replaced that)
I then start it back up and rev the living **** out of it to try and clear any blockages... she then runs okay. It's a very annoying intermittent issue... and it seems to happen on the same damned roundabout every time! At rush hour! Must give everyone coming home from work a good laugh. "Oh it's her again."
Apparently it's not the cat, but I'm having everything looked over anyway. I replaced spark plugs and tested all cylinders and coil plugs. Also had diagnostics done, no codes or faults at ALL!

If anyone has experienced this and found the issue, I'd greatly appreciate knowing!!

I'm stumped!!

Thanks in advance!