What i think is an exhaust rattle has been getting worse so i tried tightening up the heat shield with bailing wire until i can get some hose clamps. It only happens when its revved up (dont have a tach) . It doesnt happen at idle but when im at a steady 30mph it happens pretty badly. Sounds almost like a piece of tin rapping against a metal fan. Can anyone help. 2.5 4 banger 180,000 miles

 

Tap on the exhaust pipes, cat and muffler with a rubber mallet or wooden stick to see where the rattle is.

When you burn gasoline(H) with air(O) one of the byproducts is H2O(water)
This is why tail pipes drip water, and why exhaust systems RUST from the inside out

So your rattle may be a rusted out muffler or Cat, internal rattle, which would come and go with exhaust flow, i.e. engine RPMs
Internal rattles will eventually cause a power loss because parts will break off inside and start to block exhaust flow, so if you notice a loss of power at higher RPMs that has started to happen