These may be tough to locate, but PFR7B works great with all tunes: http://www.hstuning.com/product_info.php?cPath=24_32&products_id=3688&vpath=30_31Amazon UK seems to have them: http://www.amazon.co.uk/NGK-PFR7B-Spark-Plug/dp/B001MU5JB2Only plugs to work with some aggressive tunes I've run recently.