Insulation, Radiant and Vapor Barriers - Insulation outside walls

Can I put 2"inch foam insulation on my outside walls to increase my R-value instead of ripping down my drywall and vapour barrier which is like paper thin and I have 2x4 walls only so I can get more R-value outside with the foam? Please help.

i added 1 in to the outside of my home in 1995 also a vapor barrier to the outside of that and then rebricked to exterior of my home, no problems to date. so I say go for it. it made a great change in my utility bills for the better.

if we're not supposed to eat animals why are they made out of meat?

Sorry, missed this one. I'm in the process of adding 3 1/2 inches to the outside of my home and can give you tips on trim and related obsticals. Basically it is the place to go with 2x4 walls, especially if you want new siding anyway. I'm moving my new windows to the outside and trimming the deep frame inside. So far they look great. I'm working my way around the house one window at a time and leaving it covered in house wrap. Will apply siding if we get a warm spell or wait to spring.

Any questions, PM or post, glad to help.
Bud