orange engine light, at end of tether now

[T-Pot]

Can anyone please help

i have a 2.7 200 boxster, which i bought privately.
i was told when i bought it, it had a faulty o2 sensor, and the light may come on (it was off at time of purchase)
sure enough the light came on later in the day. (i believe it was prob cleared just before me seeing the car)
changed the o2 sensor and checked codes when the light came on again, and had multiple random missfire on 4,5&6
changed the plugs this weekend and 1 coil pack, as the end was broken. also changed all other coil packs from side to side to see if any code would shift side of the engine. the light has just come back on now, and again showing the same faults.
random multiple missfire on 4,5&6

what can it be? ive had it on a 60k diagnostic machine and it only showed the same faults again.
im starting to think ive been sold a lemon here.

the car had an IMS failure which was sorted, and supposedly this light showed up after the rebuild and i was told, the previous owner was told by porsche it was the o2, but of course having changed that, its not.

can anyone please help before i leave this car parked somewhere dodgy open

just to add, the cars appears to drive fine, and i have not noticed any missfire or seen any drop in performance etc

[ppbon]

The engine misfires can be as simple as a loose connector to a coil pack.
Make sure that each plug is secure. You'll hear a click as it locks in place.
The 4-5-6 bank is the driver's side of the engine.
Happy Boxstering,
Pedro

[BYprodriver]

Porsche says antiseize on sparkplugs can prevent proper grounding & cause a misfire!