[Glosboxster]

Please can you assist on the following folks?
Boxster started misfiring.
All was good, engine was running strong, slowed down into a junction and when I came out the engine was missing a beat.
It pops and bangs. Judders. Doesn't rev clean etc.
I have got one of those cheap code analysers and with the engine running it told me cylinder 3 was misfiring. I changed the plug and the plug coil but I have the same issue.
I then turned the ignition on without starting the engine and the analyser states "random multiple misfire detected" and when I scroll down it states "cylinder 1 misfire detected" ditto cylinders 2 and 3.

Just so I am not barking up the wrong tree I am assuming cylinders 1,2 3, when you look at the car from the rear are on the right hand side and cylinder 1 is the most forward ? Yes or No.
Is there a common part for just these 3 cylinders that could be causing the issue?
Has anyone had a similar issue and if so what was it?
Any assistance most greatfully received.