I have old ATR wastage and downpipes, the last couple of days out my wastage reading on scan master was reading 80.2% at 28-29 lb boost but before it was reading 97-100 % at 30-31 lb boost, any reason why this would drop? I would like to keep boost up in 30 lb range, Before i did tightened down nut on the spring and it did raise boost up allitle to 30lb but it read 100% also.Maybe it is time to replace wastage or if possible get parts for it, any help I would appreciate it thanks