Rules smell? Of what, stale sweat or blossoming roses?

Of course modified gear affects game balance. If there is no difference between, for example a stock blaster pistol and a heavily modded one, there's something very wrong with how you balance combat encounters. The base stats for a blaster pistol is Damage 6, critical 3, range [medium], 3 HP and Stun Setting quality. Now give that blaster a fully modded actuator chamber (fully modded, for the sake of argument), the Superior attachment and a Multi-Optic sight (also fully modded). Suddenly the base stats become Damage 10, critical 3, range [medium], Pierce 2, Stun Setting, generate one Advantage on hit, remove 2 setback dice for environmental effect, add two skill ranks in Perception and add one setback die to hit. That is an very powerful weapon. A player with that weapon would be significantly better off with it than he would be without it.

Oh, and accusing those who disagree with you of having "underlying problems" simply because they don't share your personal opinions is the lowest form of argument.

Krieger22 you mention fully modded multiple times there. Now this is me being curious for the sake of myself and may not be truly part of the discussion. I was curious how a fully modded attachment/mod worked as far as those pesky rules were concerned (lol)? I mean does my player have to make a check before, during, after installing the mod to mod it up even further. I am a little lost on that and as you pointed out I shouldn't just blanket rule something like this as it could have significant game balance issues.

Krieger22 you mention fully modded multiple times there. Now this is me being curious for the sake of myself and may not be truly part of the discussion. I was curious how a fully modded attachment/mod worked as far as those pesky rules were concerned (lol)? I mean does my player have to make a check before, during, after installing the mod to mod it up even further. I am a little lost on that and as you pointed out I shouldn't just blanket rule something like this as it could have significant game balance issues.

Yes, they need to make a check. Installing the base attachment is automatic, but every mod requires a Mechanics check. The first one is always Hard, and then for every additional mod the difficulty goes up one level. If the character fails the Mechanics roll, that particular mod can never be installed again on that particular attachment.

When it comes to failed mods I rule that it doesn't increase the difficulty of the next check to install another mod. It's tricky enough as it is, but that's just my opinion.

3) Well I would also rule the triumph would make it impossible to disable the attachment even if the weapon takes damage or there is a crit hit that effects said weapon doesn't effect the mod that you added as it was so well integrated.

That's a penalty written as a bonus. The main time "it's so well integrated it can't be removed" would come up is transferring a mod from one piece of gear to another. The only time "stuck there forever" is a good thing would be if someone tried to steal your mod - but if they can do that, they already have the gear that the mod is attached to. So it's no bonus at all.

I'm with Donvovan Morningfire on this one. Attachments are effectively modular, and tend to be design for specifically types of weapons. Spin barrels vs. Blaster Accentuating modules. Both have similar effects, but one is for ranged heavy, and the other is for ranged light. There's already an implied difference as to how far that modularity can go. As such, transferring attachments is as simple as pulling the scope off of one gun and putting it on another. Mods, on the other hand, I see as being fine tuning the attachment specifically to the weapon or armour it's fixed to. Move the modded attachment to another weapon, and the mods are gone.

If you wanted to be particularly picky, each attachment can only be modded a certain number of times. If transferred to another weapon, the mod doesn't come with it, but the number of times it has already been modded does. I wouldn't do this myself, butif this is a concern, it could be one way to handle this.