Hello everyone, I purchased a used macvidcards flashed evga gtx 750 ti from ebay seller and having dual monitor setup work. I am having issue of not booting only when connect to 2 monitors. The weird thing is it works when I connect single monitor to boot and connect second monitor after booting. When connected to dual monitor and trying boot, it starts to boot and shows apple logo on one monitor then both monitors gets no signal and stuck there. Same results with any combinations of dvi, dp, hdmi ports connected. I have tried on different versions of High Sierra including 10.13.1, 10.13.3, and 10.13.4 with same results. Each time with correct web drivers. My system is Mac Pro 4.1 flashed to 5.1 running High Sierra perfectly with Apple oem 5770 with dual monitors. I also have upgrade to dual x5675 and 32gb ram. Thank you in advance for your help.