4.1 to 6.1.3 without losing baseband - errors 3194, 1600, 1601

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Hello. I have an iPhone 3GS with iOS 4.1. and baseband 06.15.00 and I want to upgrade to 6.1.3. The problem is that I have to keep the baseband unchanged. I downloaded the firmware - 6.1.3 (I tried 6.0 and 6.1.6, but they gave different errors), I saved SHSH blobs and I stitched to the firmware. Put in DFU, redsnow does not work. So I tried custom restore (with shift) in itunes, but error 3194 popped. I fixed hosts and I started TSS server in TinyUmbrella, 3194 disappeared, but 1600 popped, second time 1601, and another time 1602. Another day, 3194 again and after TSS server and hosts, 1600, but it comes back. I have no more ideas, I even used iREB and TinyUmbrella, cable is original. If you know how to manage without errors, I would be grateful. Thanks.