340 No low end power

Like every one has said, Get ride of that POS manifold!

My sons 73 power wagon had that same manifold. Bolted on a stock duel plane manifold and his mileage Jump and he can brake the tire loose on pavement!
before you would have to go light on the throttle, tell about 15 mph and then stab the throttle.

Nothing was changed but the manifold. Could NOT be leave the difference!!!!!!

Dist tuning is the best place to start.

I also live at high altitude.
My 340 had 24* at idle and total at 38. works pretty good for me.