If you use cheats  (legit ones obviously) in the game I know it prevents you from unlocking certain achievements, but that doesn't mean I can't unlock those achievements if I started a new game does it?

Achievement whores never prosper.

Btw, I need your Live codes, your points and your gamercard.

Lol, I'm not actually doing it for achievements (seen as you cant get them if you activate the cheat via the mobile phone) I just want to mess around town with unlimited guns and fast cars.

No.

You want the whores.

Admit it.

I used a couple car spawns, and I didn't get a 'cheat' warning in the game yet. However, I've flown under all the bridges and it still won't give me the achievement. Hmmmmmm.

Create a separate save file for you to use cheats on?

I used to do this with the other GTAs.  One file to complete the story and the other to screw around with.

I got that trophy for jumping all the stunt ramps even though i used the bike-spawn cheat, but this cheat only...