after about 5 mins of starting it up my 172 was spluttering and the zorst popping flet very strange like it didnt want to go, almost like a blocked tailpipe. I had this problem on my old valver, and no one could find out what caused it, it caused me allsorts of problems, but then it got wrote off solving it i hated that car (useless) but today the symptoms that plagued my old valver were appearing in my 172, has anyone else had this problem with their valvers or 172s my cars std apart from a magnex. grrr im starting to think SHORTY is right