I've been bashing these Chinese kits as loudly and proudly as possible, your experience is quite common with the Chinese kits/parts. Countless folks have ordered an done their carbs with them only to have to pop the rack right back off and redo them with K&L (Japanese aftermarket of known good quality) or OEM Yamaha ($$$$$). I used K&L on both my Vmax and Venture and all is well.
I got my diaphragms out the UK, there is an Ebay seller that makes them there. The full set of 4 was a lick under $100 shipped and they got stateside here quite quickly. They are a touch heavier than the OEM so I recommend getting all four.
Generally speaking, NEVER EVER put Chinese aftermarket parts on your Japanese, Euro or American bike, car or truck, or household appliances. Dont buy anything form China that touches your food, or goes into/on your body, or will cause any distress when it fails to perform it's intended task.
A few things I've noticed, especially online/Ebay.
US Seller (guy here in USA selling stuff from China) Dont be fooled by the big proud American flag icon on the ad.
Unbranded (stuff from China)
Price we want to pay vs the fair going price for quality versions of essentially anything (more crap from China)
Made from global/international materials (Chinese pot metal or deteriorating rubbers and plastics that don't stand up to time or elements, like bowl gaskets)
Packaged in the USA (made in China)
Distributed by insert USA company here, but almost certainly (made in China)
Counterfeit items packaged and advertised to look like the authentic items are also a HUGE problem. If its on Alibaba, it's almost certainly Chinese junk.
The Counterfeit items are such a problem that it has been included in our trade deal negotiations with China. A quick internet search will usually get you information on how to spot specific counterfeit items. I've had my best luck using sellers that have long histories and at least 99.9%+ feedback, then I read the negative feedback to make sure nobody has received bogus items from said seller.
I generally find that things NOT made in China will boast MADE IN USA (or wherever) If you have to search for where something was made, probably China. Sorry you had to find out this way. Sellers and mfrs can be VERY deceptive on Chinese made items, we must always be on our toes and a little DuckDuckGo search can be a great source of information on how to spot quality vs Chinese items. Very sorry your going through this, is it up and running now?