Hi. My Dad has his 2nd BMW! He had an X3 and decided he wanted an X5. He’s a bit of a boy racer at 77! Anyway, he’s only had it a couple of weeks and it seems to lose power occasionally. Not every time he drives it, not only first thing in the morning, just as and when. A BMW specialist did a thorough computer test and no faults. No warning lights. Drove like a dream on the test drive. He told my Dad it’s most likely it needs a new particulate filter and quoted £3,000. My husband is a mechanic (40 years experience) but mostly fixes classic cars. Any advise would be greatly appreciated. Many thanks.