Ya that sounds like something could be wrong somewhere. I know you've been trying lots of
settings etc.. and hearing a gigantic earful from everyone but....
The next time you have your detector in hand outside, try finding a complete target/trash free
piece of ground,(use DC mode to make sure) , ground balance, then lay a quarter flat. Put in 3khz and AC to max with PreAmp 4 , and see how far you can detect it with good sound. I know it may
be unstable, but just for a test of how far it can reach it. That should tell the tale.
Today I detected in my own yard for the first time with it REALLY cranked. AC 85 ,PreAmp 4, VDI 88
and it was surprisingly ok. When the coil is up off the ground, its gets unstable, but while detecting,
it was smooth. I located and pinpointed several targets that said 11 to 13 inches, but it was about
dark and starting to rain. Ill check those out tomorrow

I am fairly certain my stock coil was very erratic at waay lower settings, so it may be more sensitive to EMI...
I think you found your own problem though, if you can only air test at 6 inches or so. Heck I think some peoples pinpointers can almost do that. Keep us posted !! And dont get frustrated, we will figure this out ! Im glad you started this discussion, it is really beneficial for everyone to see why many forums and websites all have such different results , opinions and finds from person to person, machine to machine etc. Nobody with a new machine, has any way to know if what they are experiencing is right or wrong, or good or bad. Sharing information is the only way to help.
Not really sure why all this information seems so secret. Easier book sales when nobody knows WTF is going on rotfl