OK, did the dpf and cat deletes, now have a strange hissing noice out tail pipe. Sounds like a leak in muffler. The same noice you would here if you had a tiny hole in muffler. Really sounds strange. Any ideas?

 

I heard the same hissing noise for the first time today too. Only while I was at an idle. I did not delete the cat though.

 

I did a little research and apparently when the coolant temp is below 180 F the exhaust brake turns on and you get the hissing noise from the exhaust. I am unsure if it is cold where you are but where I am it was 26 F this morning.

 

Hissing from the exhaust tip is OK. Hissing underneath the truck is not ok. Be sure you check your exhaust clamps. I have a FLO PRO and have nothing bad to say, but, I highly recommend that if you have the ability weld the piping vice clamping it.

Lets be honest, who cares if you have to cut it off 5 years down the road. HaHa...

 

Ya, it is in the 50-60's here in south houston. Seems to do it all the time. Of course I can't here it going down hiway, I can here it going thru town with windows down. It sounds sick. Mileage has gone from 14-15 to 20-21 on road after all deletes though. Just don't like the sound.

 

What power setting do you run at?

 

Running on the mild setting. Driving easy on the go pedal.