1. They will always be able to tell if you have modded, even if you format it.

2. Yes, it will have all the achievements you modded.

3. Modding gamesaves isn't that much of a big deal and there's a very low chance of getting caught modding them. (I do it all the time, not been suspended once.)

Hope I helped

Thanks for the reply guys helped me a lot!! ive modded my gamesaves mod warfare but if i start a new game on a new profile resign and hash put it in mine will it stop the ban hammer do ya reakon or put my original one back in??? oh when ya say banned is that from total on line xbox live or just modern warfare ? and i modded my chevo's on mod warfare like a plank but swicthed the times and dates about did the womans too so she aint gonna be happy with a ban ha ha flying pans N pots me thinks ha ha thanks dean n kill-seth for the replys and kill- seth you are good at all this aint ya love ya tuts and posts N stuff did ya teach ya self??? goood on ya !!!!  Best option is new account cancel me main one and play on ?? safest i quess ? thanks in advance oh i havent been on line with the modded chevo's yet so cant i just format N wipe the lot?

Thanks to everyone who posted replys .....