Flowmaster 40 Series. Gmc 5.3l

[GunMetalGM]

Hey, just wanted to know if a Flowmaster 40 series will help or hinder my truck.

[GMstrong]

Will add sound but little to nothing performance wise.Flowmaster does the exact opposite of its name.

[tyhuck]

Yeah, Flomaster actually restrict flow because of the baffles.

[Stevens03]

Well, I've had the 30, 50 then 40 and wasn't happy with any of them. They rust to fast, and they drone alot, epecially when towing. My experiance was with a dual rear exit and on my 03 5.3, I lost low end torque. Just not enough back pressure. It won't hurt anything, and will sound good outside, but it will drone and if you use a dual exit, you'll loose some low end torque.

[scz71864]

x2 to all the above answers, FM is known as a cheap easy way to add some sound to your truck. they are also known to rust really fast. if you want performance i would go with a borla or a magnaflow. they are more expensive but worth it in the long run.