if timing is of would that give me a exhaust leak sound or what because that would save in changing the exhaust gasket wich is a pain to do \lot of work what i understand

 

Ignition timing won't change or cause an exhaust leak.
Get uder the truck and check for leaks with the engine running and feel for pressure escaping and black color signs.
Exhaust manifolds could blow a gasket.
Also listen for a leak at the back of the heads and the firewall, assuming a v8. There is a cross pipe with a valve on it that rusts out.
A hose to the ear often help locate in difficult areas.