Is my phasing out ?

I just installed an SK T-90 bridge pup in my Tele (it sounds awesome on it's own !). However in middle switch position the volume is much lower than when I have either pup selected on it's own. The SK had yellow and black wires, and I just matched them to the stock yellow and black wires. Any help would be appreciated, Thanks.

Yep; you're out of phase. You'll have to reverse wire one of the pups, and don't forget to change either: a) the plate ground wire if you RW the bridge, or b) the shield ground wire if you RW the neck.

I was pretty sure, but I thought I'd ask the pro's before I go rippin' apart again. Thanks again !

That did it ! Thanks Kevin !