I have a boost cut at 5000rpm and cant figure out why? last night I managed to get it to 6000rpm but as I slowed down for a traffic light, heard a pinging sound like a tin can and after this the car ran like it was on two cylinders,having to keep the revs up to get it hm-it doesn't idle and just cuts out after 5 sec's-i've changed the points and leads and checked the hoses and pipes and there doesnt seem to be any loose or disconnected??? anyone had this problem???