decieded to install an alternator on the race car..used a constant voltage regulator and a factory alt. after installed, charged fine BUT, the tach went crazy!! it now idles from 4000 to 4200 rpm and when you raise the idle it goes outa sight!! someone said to use a "noise filter??" on power line..would that be on the tach line or the power line to the msd??..have seen both described..help!!