Check Engine light code 0705

I am having a problem with my check engine light. It keeps going on even after having it reset numerous times. The code is always 0705 which is the evap control system. From what I understand this can be one of many problems, the most common being the gas cap being loose. I was driving my car last night and noticed that the light had just turned on. I pulled over and checked the gas cap and it was on there tight to the point where it's almost hard to twist off. I make sure it is tight because i've has the light turn on because of it being loose before. I just took in in for an inspection the other day and it passed with no problems. I'm not sure if this test is only in NY but they check the gas cap for problems in the inspection and my cap passed which leads me to believe that it is something other than the gas cap. My question is are there any tests I can do to figure out what the problem is? I also have a short ram intake but I don't think that would affect it. I also have iridium plugs. It still runs great. The one thing I love about the Maxima is people under estimate them too much. I raced a 350 IROC-Z last night and took him without a problem so it's not affecting the performance. I also have a friend that goes to an automotive school and they have an $8,000 snap-on computer which reads codes and clears them but I'm not sure if that will read exactly whats wrong with the system. Or does anyone know how much it will run me to bring it to a mechanic to have them figure it out?

Nissan dealer in this neck of the woods charges just under a c-note to read (not clear) then usually wants to charge $600-$1K to fix what they read.
Have you tried new gas cap? Cheap elimination.