Just had a look at your wireframes-

1: While it is true Max (not sure so much with GMax) you have modifiers to reduce the poly count, it is always better to be able to do mesh reduction yourself as you have total control- weld is your best mate!

I assume those pics are WIP as you still have a line where the model has been cloned and mirrored, and you could simplify the sides of the Feisar if you do not intend to use those polys- however I think you should try to break up the solid triangle shape a little. Plus try a 4 or 5 sided cylinder for the pipes- will look the same but has less overhead.

2: I cant really tell but I dont think (on the underside) the pipes or the long, thin strakes on the wings are attached to anything. Most professional meshes try to have everything connected so the mesh is 'closed'- this helps game engines as otherwise it causes problems with shadows and other artifacts.

The prototype is an interesting shape, sort of AG meets Piranha. Keep at it!

BTW, is Blender any good for games development?