I have been having some issues recently with my NA. When out in the car, it will have an occasional misfire/stutter around the 2.5 - 3k mark which goes away as you accelerate, The car also used to have a lumpy idle and cut out and has recently been fully serviced which found the Air Filter to be rather dirty. I have had the Coil Pack replaced with a good condition used one and after the filter was cleaned, it no longer hunts/ cuts out.
However, I was out today in it and it felt extremely sluggish up to around 60 mph and then when restarting the car and driving it home, it perked up and was back to normal?
I don't quite understand what is happening! Is there anything else i can check?