Will taking the cats off of an LS-1 hurt the cars performance as long as the O2 sensors in front of the cats are left?

 

no, but it will throw a code if you don't get o2 sims or have the codes removed from the pcm.

 

Speaking of o2 sims check sig

 

LOL thats great!

No, in fact im guessing that removing the cats will increase exhaust flow and performance. Not drastically, since its the stock manifolds, and stock ypipe that are really to blame for "hold up", but im sure it will be somewhat helpful.