Lets keep it realistic.. you are gonna struggle to beat 5sec in a FWD 
and 5.5 secs is 
If you can do it in 5.66 with no mods... i would expect 5.5 to be quite achieveable with an extra 50bhp and a carbon fibre bonnet and a few other mods... i am sure Hurdy will fill you in when he catches up with this thread.
Yup, R32UK is right. I made 5.66 secs 0-60mph last year at Inters completely standard. 5.5 should be easy with mods.
I guess we'll have to see this year at Inters as I know that there will be at least 5 modded ED30's there and Awesomes GTI too. a 5 second 0-60 is probably a bit over-ambitious even for the Awesome car.
The only way to get the power down better is to have sticky track rubber and even then you'd have to still feed in the power.