Engine Performance Mods - Project Sonic Boom. Helping the 1.4L turbocharged four churn out some more ponies. HOT ROD Staff Writer Feb 10, 2014. See All 24 Photos.

Diesel engines already have a growl to them, but if you want to take it to the next level, here are five ways you can do it -- no matter your budget.

First of all, play this short video and just listen. That throaty growl under acceleration is the result of the cold-air intake. It sounds great on this VW VR6, but it was even better on my 1.8T ...