What all do I need for a 2.1L KB on Stock 03??

I think he is talking about the 2.2L kit.. thats the bigger KB or (blowzilla) kit..

Your going to need a forged bottom end, I would also drop the compression to the 8.0.1 range plus you will need to upgrade to cobra tank and pumps

there is other stuff you will need to but I don't have the time to list it all, I am sure other will come on and list them.
 
2.1 has everything you need to get it installed and running correctly. something to note is that you can upgrade to the KB CAI and big tube kit with 90mm maf, not necessary though. aside from that there is nothing else to be done with the blower its self. at that point its just getting a built shortblock, maybe porting heads, cams, and exhaust. nothing more to do with it then, aside from a better tune.

but the new 2.1 comes complete with nothing else needed other then whats in the box.

Torinalth
 
as long as you dont go over 420 rwhp and dont lean out you should be fine on a stock bottom end. you will be on borrowed time once you go past 400 from what i've been told. i'm about to put an IC on mine and then push it to 420 so i'll let you know how it goes.