Hey guys. Just picked up my 1975 z last month and it runs great for the most part. It has a rebuilt 260z engine twin carbs and a header. I drove it on the 60 mile drive through lake havasu to kingman az and it ran great till I got back to town and had to go up a hill and it would seem the exhaust note would get louder and back fire and I would lose power to a point where I'd have to pull over goin up hill. It would stop between 3-4k rpms and then get weaker the more I try to push it. Just changed out the dizzy cap n rotor and plugs n wires so now I'm thinkin its a tank pump or filter issue. Any input would be great. P.s. I did do some searching around but its tough findin something relevant to this model. Thanks in advance guys