Keyword Stuffing + Content Randomization

I have been getting mixed opinions regarding keyword stuffing and weather it works, doesn't work, or will flat out get me banned. I understand that including the same keyword 100 times does not do any better for me than just including it a few times (say I spam "funny videos" all over my blog). The keyword stuffing I'm talking about is using DIFFERENT yet related keywords hidden in white on white text. Say I have an autoblog dedicated to cars. I will stuff cars, fast cars, racing, honda, toyota, d16, b-series, motor swap...... basically anything and everything related to cars. This works for craigslist ads, however I am not sure how well it will work in terms of SEO

As far as content randomization goes I will be primarially scraping my content with my modified version of WP-Robot (I need to scrape sites praticular to my niche) however I am worried about getting penalized for duplicate content. Assume I scrape a youtube video and all it's comments would it make sense to replace some spaces with underscores, tack on some puncuation, replace certin words with their synonyms based on a simple dictionary, and replace the username of the commenter with a random one chosen from a dictionary? The purpose of this is to generate "unique" content in the eyes of Google's spiders. Will this strategy work or should I just save myself the effort and stick to standard scraping.

I just need enough SEO to get a decent rank then flip the site. I could care less about the long run.

Any advice guys?

Whatever you do don't use white text on white background! It's a thing from the past (it worked 10 years ago?). Now Google will detect it immediately. As for stuffing keywords in your content... you can do it. It will make your content crappy but you will rank for those keywords. Just don't overdo it.