Is straight piping bad for your engine?
A straight pipe, for example, can cause exhaust gas velocity to increase. This will likely reduce engine performance below 2,000 or 2,500 RPM, making your vehicle a little slower to launch from a stoplight.
Putting straight pipes on your truck, or decreasing your “back pressure” will not hurt your engine or performance.
Beside this, Will removing muffler damage engine?
In most cases, a muffler delete system or a set of aftermarket mufflers (or axle-back mufflers) may do more harm than good and result in less horsepower.