I am a Fox fanatic. Sounds like the low end is rich. You should start by getting it leaned up. When fuel comes out the top of the carb on acceleration this is an indication of being rich. A god way to check if you are getting close is the pinch test. Get it to idle around 2,800 and pinch the fuel line shut. If the engine runs for a while without any change and then increase RPM's it is rich. If it immediately dies then it is lean. You should be able to pinch it for about 1 second before it increase RPM. This would indicate you are close. Then set the top end. I always set the low end first.

I have a new MK carb that has only ben bench run that I would consider trading for your Perry setup if you are interested. I had it on a Eagel 60 series I engine and it would transition as if it had an accelerator pump on it. The mods on flightline are good but I don't think they will fix your problem. More for flameouts due to overheating. Fox engines are typically high compression. Something else you might want to do is put a colder plug in it. This will reatrd the timing a bit. This might even work in place of modifying the head if you are uncomfortable with doing this. If you want to see a picture of the carb it is the one on my engine pictured on Flightlines under older engines 60 size.