Sinister Diesel’s new 7.3L Power Stroke up-pipes eliminate the slip joint in the cast merge piece, which is a common location for factory up-pipes to leak. In addition, Sinister has removed the bellows in favor of a much stronger, longer-lasting “double slip” flex joint which means better performance and no cracking due to heat fatigue. This design allows the upper and lower sections of the up-pipes to flex and move with heat expansion while maintaining a 100 percent seal. (888-967-8823/www.sinisterdiesel.com)