I know that there is a "Reset All Stats" button, but I don't want to be all the way back at level one after getting tenth prestige. When I started playing MW3, I hadn't played CoD in forever, and I was a negative K/D player. Now I'm at least a 4 or 5 K/D player and I get MOABs like every other round. My K/D though is still only 1.50 :( Just wondering if it is resettable via mod or something.
The only known way to reset your stats is to get to the maximum prestige and use a prestige token to reset yourself back to level 1.
The stats are tracked centrally as part of the Call of Duty Elite service, so there's no way to mod your client to change them. Even if you could somehow break the system to change your stats, you'd probably end up running afoul of the anti-cheat systems in place.
The bottom line is: don't mod, hack, glitch, or otherwise cheat - even to edit your stats - in Modern Warfare 3, unless you're prepared to get permanently banned.
Statistics are statistics is, as agent86 says the only way to reset them is to do a reset all stats.
As Brian noted most people start out badly and slowly work their way upwards, eventually your stats will level out but this does take a long time. For example I started out pretty badly but now my weekly KD is around 2.1 but my all time KD is still around 1.9 - eventually I'll level out somewhere around 2.0 I expect.
If you truly are a 4/5 KD player (and quite frankly I doubt that having seen only 1/2 plays online ever with a genuine KD in that range) then you should level out quicker.
However everybody has games where they are unstoppable and get a ridiculous KD but your stats reflect your average, I have games where I may hit anywhere as high as a 10-20 KD (very rarely I might add) but I have far more games where I only break even or just over (plus a few negative games now and then) so in the end everything balances out.