Your brushing can still use some work. but i see some differences between your other pieces. that means you tryed to improve. that's good. Good use of stocks to, but some pieces look crappy, not that that is your mistake. Chaotic render to, I like those pieces but i couldn't get them on my Desktop. Nice and clean, maybe you should try that at once? Anyway overall stuning job !!
the bottom pipe thing looks kewl too btw.
nice work
mP