I just bought an 82 Z, and recently had it tuned by a race engine/car builder, and since then my 305 has been very snappy and runs excellent. I never ever kicked it down because I had no reason to, but the other day I did for the first time. It kicked down fine, climbed to around 5000, then shifted. But right after it did that, it bogged bigtime and just kept bogging untill I let off the gas. Then I tried slowly bring it up to around 120 km/h and right when the tach hit around 3000-3500 it bogged. And I did'nt even kick it down that time. So it seems like it is starving for fuel from what I see. I know the carb is perfect because it was freshly rebuilt. I had the fuel tank out, cleaned it and replaced all the fuel filters.

What I am thinking, the problem has to do with the fuel tank not breathing properly to let enough fuel through.

What do you guys think??

Thanks......