The first thing that jumps out at me is the long thin tri at the front of the shell exit. It might be wise to carry that loop around the front instead. With the way it is now I don't see it smoothing any better no matter what tricks you pull. You can control the smoothing with more geometry but it costs ya tris you might…
I'll try and explain how I understand it. Why you get those shading errors is because the idea behind smoothing is to average out the angle of the surface polygons. Its like its trying to flatten out the whole object(not really but sort of). When theres lots of extreme angles the software trys to blend them in perfectly…
If that's your high poly then you can add more loops around the areas that shade poorly, 3 loop minimum to help near 90 degree angles smooth correctly. You should run a few more supporting loops in other places and probably turbosmooth the whole thing, to make sure its has a sufficient amount of verts to light the large…
I'm from a Maya bkgd and I use this script in Max. http://www.scriptspot.com/3ds-max/scripts/hard-soft-edge I haven't had many problems with it yet. But if you wanna stick to traditional smoothing groups here, you'll need to illustrate how you have your current groups set up to really tackle this scenario I think.