Chainsaw Repair

I'm looking for some help on diagnosing a fuel problem on a Stihl 020 AVP with a Walbro WA-1 carb. To start with, I installed a carb kit that was probably China made because the Circuit plate gaskets and diaphram did not fit. After a couple times trimming and fitting the gasket and diaphram, I finally got the saw to run but when I go to installed the air filter, it will start smothering or flooding out and you can not adjust the carb to compensate for it. The filter is clean and not the problem (It has one of the nylon screen type filters). It does the same thing with just the filter cover without the actual filter being in place. You can make it do the same thing by just moving your thumb or a flat piece of metal close to the carb while it's running. When you get somewhere within 1/2" to 3/8" from the opening of the carb it will start smothering down. It seems to have quiet a bit of fuel blowback but at the same time, it has good compression (my gauge is broken so I'm going by feel) and the exhaust is clean and open. I installed a new OEM Walbro kit yesterday and it adjusted out and ran great as long as nothing is close to the inlet side of the carb. Put the breather or cover on and it does the same thing and starts bogging down. Anybody have any suggestions? Thanks

trappermike; thanks for your reply. Yes they are very temperamental saws but between my cousins 2 and my 2, I have kept the 4 saws going for years, two of them since they were new. I, like yourself, have worked on 2-cycle engines and raced them for several years (55+-) and have saw a lot of problems but nothing like this. I've had them with enough blow back to wet your hand if you held it in front of the carb and you could adjust them out and get them to run. I did install an original Walbro kit and it improved some like I said. As long as nothing is in front of the carb, it runs great but as soon as something gets within 1/2" to 3/8" of the carb air inlet, it will start smothering down. I can make it do it with just a flat steel plate, my thumb, anything that interrupts the air flow. I am leaning toward the one-way diaphram gasket in circuit plate. For right now, it's going to take up shelf space for a while until I discuss it with some more people and hopefully get some more ideas. Someone has had this problem before.