No still have the stock tach. I figure it's probably off some, but I've determined the sound I'm hearing isn't valve float because I knew exactly what Roland was talkin about as soon as I read it from other Mustangs I've had. I figure if i was runnin rpm's too high I would get valve float not a popping sound. Not like backfire either never does it under 5,500 rpm. Runs great and pulls hard up until I hear that sound then it just looses power. I'm sure rev limiter doesn't make that sound I've hit that a million times on other cars. I've backed off timeing, bumped up FP to 42# with vac line off, new plugs, newer MSD wires. I was wondering if the spark might be arking in cap at upper rpms? If anybody has any other ideas let me know.
Thanks