[Shotimes] Broken Bolts?

[Shaun & Meggen Livermore]

Hey everyone,
 
Today I ripped off my old (stock) exhaust system. I'm getting ready to
put on a new high-flow Dynomax one.  I had a little problem getting the
Y-pipe off though.  While I was taken off the bolts that connect the
Y-pipe to the headers, they all broke.  I soaked them on four different
occasions, yet I still broke three out of the four.  They were so rusty
the threads could not be seen and the bolt-nut assembly appeared to be
one.  I cut off the remaining length of the studs in an attempt to drill
through the bolts.  I'm hoping that if I just drill through them I can
place all new bolts in there and problem solved.  The question I have is
if anyone knows a better way to do this.  I tried drilling through it
with my 12 volt cordless, but didn't even budge.  Are there any special
tools that I need, and even any special steps that should be taken.
Thanks a lot!
 
Shaun Livermore
91' Plus 127,000 miles