I want to do my exhaust installation by myself (or with a friend), I have access to a lift and tools.  I tried to do it today and the bolts are really on there.  I sprayed WD40 all around, but they still won't budge. How long does the WD40 have to stay on there? How much do I spray?

Can someone who has done it explain? I have a 98 240, thanks.

do u have an air gun with some torque?
well u might have to just cut the stock exhaust... there is a little trick my friend does... he use a chizle like tool or a jack hammer like one... and he just cuts the old exuast off and it still can not turn the bolts then just cut the bolts.... ]

u need alot of WD-40 ,u can not really hurt it, but alot and a while

to prevent this from happening again, use stainless steel screws and bolts and put on AntiCeize

To get your stock bolts off you will need to use a breaker bar. Just go buy a metal tube that will fit over your socket wrench and make it a little longer so you can have more torque. And let the WD-40 Sit on there and soke it on there. And like drifterx said use AntiCeize. Its some good shit.