I have a 07 35 and just had an isimple ipod adapter, Avital 5303 alarm with starter and my amp and box with 2 12s. Ever since then, every time i'm on the highway and the rpms are steady for awhile when i let off the gas the tach will hover where it was. It will eventually come back down slowly. The alarm is 2way. Could it be that the alarm frequency is interfering with the tach? Anyone have any ideas?
http://www.avital.com/products/Product.aspx?id=5000
http://www.avital.com/products/Product.aspx?id=5000