SammyJ
New exuast new, cat ,new spark plugs, new leads new, pod , changed oil, new filter......lots of dyno runs.....thats a lot of money...........
Why dont you ask your cousin, the person you bought the carfrom, of its mods???
That way, you'll know what other work has been done (maybe internals) and could link that too the problem?
Maybe the car was advanced something crazy, and during your last dyno run (after which your car started playing up) the guys who performed it, made the car ping to the bullshit, causing some internal fault?
Stop wasting money on relacing stuff that you may think it is. Get it looked at seriously. Given the good once over..........unless that is, you have lots of money to do that stuff. lol