Glad to be of help. Re BMW airhead valve parts l have found Swiss made intervalves and elco guides to be the most durable and long lasting, change at 50k intervals and avoid the heads breaking off! Agree there are some awful pattern parts as well, AE probably the worst with incorrect machining of the collet grooves. The elco guides are a tad longer which can only help in there longevity, PCV got it right with the two guide system, less potential for guide wear. Happy fettling!