So here's the story, bought an FJ40 from California that was originally from Wisconsin, PO had bottom end rebuilt, head, etc. I bought it, trailered it home. Ran like s***. So I have been doing all the things that needed doing: adjusted the valves, reset the timing, had huge vacuum leak because PO had no PCV valve, replaced that, replaced the diaphragm for the secondary barrel. Checked the vacuum with a guage and it's that's great. Still runs really poor. When I am out on the road trying to get up to speed it hesitates like flat spots and like the fuel delivery isn't up to par, and when I hammer down and the secondary barrel kicks in it almost always backfires back through the carb. The PO said he rebuilt the carb, but his poor skills of assembly point me to assume he didn't do it correctly, so I guess the only thing left I can point at is the carb needing a good rebuild, what do you folks think??? Any help would be greatly appreciated!