Guys, to all those that commented thank you, I took the newly replaced coils off again today, and took the cap off, although they tested up ok with the multimeter they looked fairly worn, trimmed the ends and replaced, checked all over leads but still seemed to that dead spot, noticed pipe 3 was cooler than the rest, kept on tinkering, tapped each carb fairly hard then the engine started to idle better, revs seemed higher, put the tank back on and decided to give it a razz down the bypass. Definitely a huge improvement, I'd its sorted or not I ain't sure yet as I was still getting a delay on pick up, so all the things I tried were coil pack swap x 2, 4 x spark plug swap, liquid molly additive, checked all cables running to the coils, trimmed coil pack leads by 5mm and re fit and also tapped all carbs with a screw driver. I did notice when I got home that pipe 3 was definitely hotter than it was previous, but not as hot as the other 3, I have now put some new fuel in and hoping that it runs through and sorts the issue. Debating if it's worth running more liquid molly through to may dislodge more dirt?
Tha ks again.everyone