start by changing your sparkplugs, or even just check them that the tips are not bloked if still ok then just send them back in, if it does it again try doing a diognostics check, that is if it does...
iv used king springs on my old previous rides and believe it or not they sagged after 2 weeks...it started scraping at places it would have scraped when first lowerd...get yourself a nice set of...
$950 is way too much, ask around there are other people out there that will do the same job and charge way less...upto you if you want to ruin the warranty if there is any left...
i used a exedy heavy duty before and it had a reasonably hard pedal feel, now im running a exedy Sports organic and it feels the same...it shouldnt feel that soft, was it a brand new kit installed?...
added a rear ITR swaybar on my eg b18c and i felt great stability at high speeds, before i had it on the rear wouldnt be stable in cornering now its much better and was worth every penny.