Running Problems

[KTP]

have some issues with my Octy, its a vRS and fairly recently had an issue with a coilpack, i was heading to Southampton from Edinburgh when one of the packs packed in about 100 miles from southampton, so i had to drive back home running on 3 cylinders basically.
i had just picked up another RS so the injured one got left in my drive for a few weeks unused. i replaced the coilpack and it was back to running on 4 cyl and i thought my problems were solved.
however, at the moment it's horrendous on fuel, i'm getting 22mpg on motorway runs and closer to 15mpg around town and it has a severe lack of power, i can feel the turbo spooling up but the car is extremely hesitant, i've checked all the pipes and cant see anything wrong with them, i did however replace two pipes on return from southampton as i noticed that a couple of them had burst, seem to be the common ones at the top of the engine.

in an effort to rule things out, i've started swapping parts from one car to the other, swapped all coilpacks from my good car as i know its running sweet thinking maybe one of the other coils was on its way out but didnt make any difference.

the car feels ok at low revs, no misfires, just when you put the foot down a whole lot of nothing happens and you can sometimes hear the turbo building up then it dumps without lifting the throttle.

anyone experienced this? i've tried searching for all sorts of problems but unsure what to do. have thougth about swapping N75 valve from the other car incase its that as i've read that can give some hesitation issues but havent seen anything about it having such a drastic effect on the mpg. 
 

[octyal]

does it improve if you unplug the air flow meter? (the TC light may come on when you do)

[KTP]

No, i took that off and cleaned it but made no difference, runs worse with it unplugged also so i think i've ruled the MAF out.

[sharkrider]

coolant temp sensor for the ECU, try swoppping that over.

[Ootohere]

When the Coil Packs were failing what was the condition of the spark plugs when checked / inspected and the gap checked?

& were they then replaced with the correct plugs correctly gaped or were all 4 of them as they should be?

[mac11irl]

Possibly stupid question, but has the coilpack recall been done on either/both cars?

Have you checked the sparkplugs? Could the cylinder just need to dry out after pumping not burning fuel through itself for 100miles.

Also, worth fault scanning if you can..