Re: running so oddly...?
sounds like you may be mixing too much oil- when it's hot and running it overides the fouling? Might explain the poor idle.
usually it is carburetion- billet intakes work much better than standard intake- I'd try thinning the mixture first- if that doesn't work you can always put more oil back in the tank.
a lot of people drill some extra holes into a stock air cleaner- but it sounds like you are choking down- I at first regulated the fuel a little bit- crudely- with the petcock- but a billet intake ended all my cab and 4-stroking bog down problems- 66 Speed carbs work well too- one or the other, or both- try the cheaper billet first- like $17 now shipped at Pirates