I agree with you, that the M3S90 shouldn't one hit even on body, but changing different stats, which all change nearly the same isn't the right way to approach this problem.

A delay of 1.7 along with all the other changes is pretty unbalanced: The auto shotgun has a delay of 0.8, so theoretical you can shoot 2.125 times with the auto shotgun, while you shoot once with the M3S90. This would result in 187 damage for the auto shotgun, while the M3S90 would deal 98 damage with the suggested stats, but has a significant lower hit change, caused by the extremly higher cone and one bullet less.

So my suggestion to fix this issue:

SWEP.Primary.Delay = 1.4
SWEP.Primary.Cone = 0.12
SWEP.Primary.Damage = 13
SWEP.Primary.NumShots = 8

Old theoretical damage: 104 (M3S90) vs. 132 (Auto Shotgun)
New theoretical damage: 104 (M3S90) vs. 154 (Auto Shotgun)

I haven't tested these stats, so what do you think about it?

Well, honestly i brought the Auto Shotgun down on my server anyway.Problem is that we are lacking of players who play anything else than shotgun *.*
If i may correctly most TTT servers got this problem.
That being said, i would like to share the auto shotgun stats:
/*****************************************
SWEP.Primary.Damage = 11
SWEP.Primary.Cone = 0.1
SWEP.Primary.Delay = 1.1
SWEP.Primary.ClipSize = 8
SWEP.Primary.ClipMax = 24
SWEP.Primary.DefaultClip = 8
SWEP.Primary.Automatic = true
SWEP.Primary.NumShots = 6
SWEP.Primary.Sound = Sound( "Weapon_XM1014.Single" )
SWEP.Primary.Recoil = 8
*****************************************/
Even with this stats players still play autoshotgun a lot but to balance this out we decided to increase every other wepon a lil bit. Since recoil does not even get close to the "real" recoil such a weapon has also the recoil was being incresed.
I wouldn´t say that changing the stats like you said might help to have at least the shotgun not as OP as it is. Take a look at the other weapons in TTT. Lets just take a look at a usual Mac10:
/*****************************************
SWEP.Primary.Damage = 12
SWEP.Primary.Delay = 0.065

Would mean a theoretical damage of 184,6 damage could be dealt.
Honestly waging a weapon with numbers is not a good idea since it´s just theoretical.
Did you ever saw a player hitting all hits on a Mac10? M16? Famas? |Input any weapon here except shotgun|? Well while playing a lot of hours i recognized that most players dont even touch SMG´s cause of its lame damage which will "really" be dealt. Thats simply because it´s way easier to hit with a shotgun then with a SMG or Assault Rifle. Hitting once 8 shots is easier then hitting 8 shots in a row with a short delay if you understand me correctly ;)

Thats the main issue we have on our servers.
While talking here i came up to another idea. Maybe you could release this weapon just a second time with some other stats or give me the permission to do it in your name. I´d gladly do so. As i said doin copy pasta is first of all not allowed and secondly just lame.Stealing someone´s work´s just lame. That´s why i came in here to have a talk about this main issue.
What would you try to do? What´s your opinion of this statements? In the end it´s up to you anyway. ;)

greetings Headbanger

I've tested it with inversed damage and numShots, it felt much better. Exact changes can be found in the changelog.

May i get the permission from you to create an M3S90 from your already existing one for our server? We feel like the shotgun might be still to OP.

There shouldn't be a problem, creating a M3S90 only for your server.

There it is

I made sure that every Credits goes to you. Also linked your original weapon to the item of course and announced that people who will use the M3S90 by themself shall go to your one.

Please tell me if this satisfies you :)

Everything seems fine...

Glad to hear so