my 91 2600i likes to backfire when decellerating...i need help diagnosing this issue so i don't have to take it into a shop...keep the suggestions coming...
the only issues i have with the truck is that it uses oil a bit, prolly due to valve seals cause it smokes on startup...

 

vacume leaks can cause this and burnt valves too....if you had a carb it would be very easy to diagnose....do you still have cats on it?

 

i had the cat cut out..still let's out a backfire sometimes...