[Chad Hauris]

Sounds like there may be an open coil in the rf amp/antenna circuit..had a Ford tube type car radio that would work only if the antenna were connected to the converter grid. There was an bad solder connection to a coil in the RF stage.
Double check anything in that circuit.
If it is working right, pulling out the RF amp should stop the signal, so the only way the signal is getting in is in a roundabout way.

If there is noise...have you eliminated all causes of man-made noise such as touch lamps, lamp dimmers, fluorescent lamps, switching power supplies, etc.

Also how is the alignment of any trimmer capacitors in the broadcast band RF or antenna circuit?

If you have an RF generator, set it to the modulated tone and use it to introduce a signal and vary it to different frequencies and see if the test signal is picked up. It may be good to double check your IF alignment on broadcast bands too and make sure the adjustments are peaked for highest amplitude.