If you take out your catalytic converter in your truck it is likely it will send a code, i've heard off people putting off-road (catless) H or X pipes in mustangs and getting check engine lights and when the check engine light comes on the computer automatically cuts out timing and starts dumping fuel which is likely to kill any catalytic converters left in the exhaust system (they would overheat, melt and plug the exhaust). If you want to make your truck louder, get mandrel bent (without dimples) exhaust custom bent to match up with the cat-back exhaust system (same diameter pipe) you have and have high flow cats instead of the restrictive stock ones. Reducing the bends in the exhaust will increase flow and will make the exhaust substancially louder and deeper.
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'84 Mustang 5.0 LX
My car