Thanks for the replies. She has only covered 70,000 miles so low miles with full history. Plugs were changed 4k ago along with all filters, MAF cleaned, TB cleaned etc. Sometimes it starts fine with no kind of 'misfire' I say misfire as this is how it feels. The past few days she has started fine......Strange? I never knew about HG being a common failure on these engines.....Can but pray its not one as they cost a fortune to fix.