(2) you remove the intake manifold and either spend acouple days chipping carbon out of the crossover passage or take it to a machine shop that can put the manifold in a machine and/or chemical solution that will clean it out.
The "heat riser" in the intake manifold is more accurately called the exhaust crossover. As the name implies, the crossover allows exhaust gasses to pas from one head to the other through the passage in the intake. The purpose of this system is to improve fuel economy and driveability by ensuring the intake manifold gets hot enough for proper fuel atomization. Lots of aftermarket intakes don't have the crossover because the intakes are designed for "performance" applications, not daily driving. Hot intake manifolds theoretically hurt performance because the air/fuel charge is heated but colder air makes more power. But running an unheated intake on a carbureted vehicle is folly if you use it as a daily driver on the street.
You need to make sure the heat riser/heat flapper in the exhaust system also is functioning correctly. I must be free to move and properly installed.