Started having a problem recently, iv noticed that theres a missfiring sound and abit of hesitation just as the turbo spools up, it mainly happens in thrid gear but can be driven through untill about 6500 rpm when it starts missfiring again
The was mapped a few weeks ago and overboosts to 20 or so psi then holds a constant 15 or 16. I went to replace the spark plugs with Ngk iridiums the other day with an untouched gap, however i found that the car already had denso iridium plugs with a gap of 0.65 mm, The ngk plugs made the missfire a whole load worse when it came on boost and coughed and spluttered all over the show
I also find that around 5000 rpm in 5th gear the car makes a rather loud backfire and looses all power especially when going up hill (down to more load i assume)
Anyone have any suggestions as to what this could be?