#1
Ok, so I know I'm gonna get flamed for this or whatever... but bear with me...

I bought an old washburn stealth from a guitar center a while back and decided to fix it up.

I put Guitarfetish crunch rails in the bridge and vintage 59's in the neck. They both sound great by themselves but when I flip the switch to the middle it sounds some kind of aweful. The harmonics are non-existant and it gets muddle and loud.

Reason being that the neck pickup has an output of about 8 k-ohms, where the bridge is about 16 k-ohms, and the difference in resistance and output makes the mixture something aweful.

Any thoughts about how to better balance the middle position of my swithc?
#2
First make sure they're running in parallel, and not series and also check the phase (I doubt this is a phase issue though as you said it was loud).
#3
You want a more powerful bridge pickup because the strings move less there, so they ned a stronger magnetic field to induce the same current into the coils. Phase seems to be the problem other than volume as Pyro said. Check that you didn't **** up the switch too.

edit: the dime series washburns are badass, it's the deans that blow.