my sho is banging out and back firing through the exhaust and my tach is going crazy at the same time , it only does it when im getting on it and at about 4000 rpm , any other time it drives great at normal accelaration any ideas

Welcome to the forum!

Sounds like you might have an ignition module issue since the tach is going crazy. The Crankshaft Position (CKP) Sensor is another common issue on the V6 SHO, but that will usually lead to stalling as well.

You should also pull the spark plugs and wires, inspecting for signs of oil in the spark plug wells. This causes the wires to short to the head through the oil rather than through the spark plugs. Another fairly common issue with the V6 SHO.

-Rod