Last weekend I flew a flight and landed and then tried to take off and the engine would die when I would advance the throttle and get up to speed. After that I wouldn't be able to start it. I changed the fuel tank nozzle because the pressure hose wasn't any good in the old one. Today I went flying again and I took off fine and flew around for about 10 minutes and the I went into a climb and slammed the stick to full throttle and the engine died. I landed and tried to start it again and it wouldn't start. I lessened the needle valve and it started up but it would surge. I then tried to advance the throttle and it died instantly. I tried to start it again and the same thing happened. Then I tried to start it again and it wouldn't start so I increased the needle valve and it started and sounded good. I then advanced the throttle and when I got up to flying speed it died. The same thing happened again. I'm dumbfounded on what to do so I thought i'd ask on here. Would the engine run if the fuel lines got crossed? Would that be possible.