.

Considering this, does changing muffler increase horsepower?

Replacing your car's muffler alone is not enough to open up the restrictive exhaust system and allow the extra airflow that increases performance. MagnaFlow, an aftermarket exhaust manufacturer, says that its customers can expect horsepower gains of around 10 percent (which is a pretty commonly-quoted figure).

Subsequently, question is, can a bad muffler affect performance? Just like you, your car has to not only be able to breathe in, but also breathe out to function properly. Bad muffler probably won't affect performance as much as a plugged catalytic converter(s).

Similarly one may ask, does straight pipe improve performance?

Street cars need good performance at stop lights and on highway on-ramps. 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.

How much HP does a turbo add?

Turbochargers Increase HP. Hanging a turbo on a small engine allows a little engine to breathe big. With only 6 to 8 pounds of boost pressure, a turbo can increase power output 15 to 25 percent or more over a naturally aspirated engine.