back pressure? You dont want back pressure in a diesel. Im a Journeyman Heavy equipment diesel mechanic. Less back pressure is louder but its better. GAs engine is different story?...back pressure?

 

For towing, yes probably it will hurt part throttle torque though if you dont have it. been there done that... when I had my straight thru setup, the motor screamed up top but had lost alot down low. with that loss was about 1~1.5 mpg. adding in the aero where the cat used to be gained me back about 1.0 mpg... at the cost of some top end performance. (daily driver)

 

The last time I saw a post from you, you were still in school so if your all done with school now how does that now make you a Journeyman heavy equipment diesel mechanic? I though it took many years on the job to become a Journeyman!