That is your PCV Valve hose, and with that being kinked like that, yes it will make your car idle like crap. Either rip the whole PCV system out and replace it with a LS6 valley cover, or just get a new hose for the PCV
pull that kinked hose off and replace it with a small piece of fuel line 3/8". I would also check out the rest of the PCV lines for rot. Probably find another hose set up ebay pretty cheap. LS6 valley cover is not necessary.....Period! Unless you just feel like spending money.