Following service last summer my 156 JTS 2.0 2005 79k miles has occasionally been giving Engine Management warnings on start up and then 'Go to Dealer' displays. I got it checked over at the dealers just before Xmas, the messages were P0300 (random misfire) and P0301 (no 1 cylinder). They swapped the electricals around and the code stayed at P0301. Action recommended was to get cylinder head off to investigate. Car sounded OK to me and I have been driving it since (2000 miles) but messages are more frequent. Car sounds and runs OK but is getting a bit 3ish on morning start up. Is it time to go to dealer for the cylinder head removal, or fill up with Redex, or is 79k miles about it for a well looked after JTS 2.0?