I borrowed some NGK Iridiums and tried them in my car today. took it out for a test drive. car never felt any quicker (not that I was expecting it) it actually felt (the only way I can describe it is 'empty')
It didn't rev so freely either.
Went back to garage and put my Bosch Super Plus ones back in. and at the same time put the top airbox cone pipe back in.
Car drove a lot better. it was smoother, tighter, and felt torquey again.
exhaust sounded better too.
I have the K&N, Vectra C pipe and Cat back Powerflow exhaust.