Twin stick 13 speed refers to a manual transmission commonly found in semi-trucks, which has two gear levers that allow the driver to independently control the high and low gears of the transmission. The 13 speed transmission provides a wide range of gear ratios to choose from, allowing the driver to optimize fuel efficiency and power depending on the load being carried and the terrain being traversed.

A straight-piped Detroit engine refers to a specific type of diesel engine commonly found in semi-trucks that has been modified to remove the muffler and exhaust system. This modification can increase engine performance by allowing exhaust gases to flow more freely, but it also results in louder engine noise and can be illegal in some jurisdictions due to noise pollution regulations.

Together, a twin stick 13 speed transmission and a straight-piped Detroit engine can provide a powerful combination for hauling heavy loads over long distances. The precise control offered by the transmission allows the driver to optimize the engine's power output for the conditions at hand, while the straight-piped exhaust system can provide a distinctive sound that many truck enthusiasts find appealing. However, it is important to note that modifying a vehicle's engine or exhaust system can have legal and environmental consequences, and it is always a good idea to check local regulations and consult with a professional mechanic before making any modifications.