dwyane and boyd jnr certainly didn't get along, possibly because when dwayne asked him to sort something out as he was using the guys for some other works he was told "it's coddingtons name across the shop entrance, not dwyanes, so get someone else"

mike was in a car with boyd when it crashed and mike's face got smashed to fuck, it's all be reconstructed which is why he can't smile and talks funny

and, apparently, foose left boyd's when boyd's was facing bancrupcy and boyd never forgave him for that act of cowardice

there are loads of other things that you pick up along the way when you've seen all 60+ episodes of the show