I have a 2000 7.3 f350 dually with airaid intake installed....Truck always seems to lose power during towing and was looking at my airair system and noticed that when the hoods closed...the Filter box is totally sealed...as seen by imprint on hood ....there is only a small square hole cut out under the filter for air supply...I know these diesels need a ton of air and when climbing hills and towing its getting very small air supply it cant be getting Max Power...Am I correct? This needs more air into it..? Plus the filter is Black with dirt so it seems to really be sucking for air...I have cleaned it many times though...

 

I think I have the same problem, I have a 6637 air filter set up, but after sand storm in no. az. it sucks when climbing hills with no load. Jcab