Seat leon randomly misfiring arghhhhhhhhhh help!!!

As the title suggests. I let my tank run dry the other day about 500m from the petrol station. so i topped it up and carried on about my business. Now my engine randomly decides to fire on 3 cylinders as and when it pleases. I have the associated P0301 code "cylinder one misfire detected" another code that i have is for the O2 sensor but that light has been on for 2 years nearly and never had a problem. So i have spent this evening changing the plugs and ignition coil with no avail. i have wiggled wires also to no avail and so finally chucked in some redex in the hope it will clean out any rubbish in the system from letting my tank run dry. Can anyone think of anything else. all i can think of is HT leads but all the shops are shit so i cant get any. Pulling my hair out over this one.

Its a 2001 1.6s with 95k on the clock
Cheers

Tom

Coil Pack, once 1 goes the rest will follow

there is only one ignition coil unit on it where all 4 of the HT leads fit into

i would start with the basics has it been serviced? if not do leads plugs fuel filters etc
the running low on fuel is a bit of a myth as the fuel dose always come from the bottom of the tank

Don't know much about Seat's but is the fuel pump located in the tank? If so it could be the problem as the petrol keep them cool and lubricated. A sudden lack of cooling could have unpleasant effects, so my old man says.