This thread is a big cluster ****, you can't blame him or anyone else for being lost at this point.
But this is what it all boils down to, no trolling: If the Cobra is in fact racing a truly bone stock SS, it's probably a solid 13.3-13.6 car, especially taking the driver factor out of it. I don't know of many 100% stock LS1's though. Most have at least the free mods or some exhaust work, which provide noticeable gains. The SS in question may be a 12.9-13.3 car with free mods and/or other work. OP doesn't even know the exact year of the damn thing, much less his setup. It's probably in everyone's best interest to assume it's at least slightly modified, if not by the current owner then by the previous owner.
Now onto the Cobra... With 4.10's he should very well get a jump off the line and from any roll easy, but probably won't with those banging Sumitomo's. The fact that he even has to ask what it'll do against a stock LS1 tells me he doesn't have much if any experience, so we can throw out these sub-13.5 times that other, more experienced drivers are running stock. And his is a vert no less.
OP is definitely going to have his hands full if we're talking realistically. Now assuming both parties are John Force-like and launch/handle their cars to the max, the Cobra on the streets should pull a stock A4 SS by a car or two.
What really needs to be faced at this point is the CAI and cat-back aren't really shit. No CAI provides signifcant gains on these 4V's and it's a Flowmaster cat-back, popular for it's sound not it's power. All the OP really has going for him right now is his 4.10 gears since the O/R X and tuner aren't even installed, and even then the tuner really isn't worth shit either.
^ I agree 100%