Thanks crasser. I did drill 20 or so holes about 3 inches up the pipe. That helped until I found the unsealed vent pipe at the roof line. I still need to dremmel the inlet as you suggested.
By the way for others who may be dealing with a similar situation, vent cap products that claim to "draw odors out" are a joke. Where would it draw from? I figured that out when I was thinking of installing a fan at the top of the vent pipe. For "air" to come out it has to go in somewhere. These tanks don't vent in the sense of a continuous flow. Air comes out when liquid goes into the tank and air goes in when u drain the tank. Other than thermal expansion and contraction and release of methane from the sewage there's no other "venting" going On!
And yes I did install an "aero" cap but only because I had it already.
Thanks again "y-all