2000 gmc sanoma acting weird and sounds like its a muscle car?

Recently My 2000 Gmc Sanomas service engine light starting flashing and the Car starting acting funny
My issues: inclued
Problem 1: When I start the truck and it really cold its like it has fat cams it sounds like a muscle car with the hold rev pause rev pause rev pause now during this my rmp is staying the same it a rough noise so it sounds just as if i had changed the cams.

What do you think will happen to muscle cars?

With gas going for over $1.30 a Liter in most parts do you think that SUVs, Muscle cars and big trucks will be the thing of the past?

Some people say that even if gas was $2 a Liter it still wont stop some people to drive their gas guzzlers.

I personally think that there should be a way to convert any car you love that has low gas mileage with a hydrogen engine or something similar.

Think this is possible in the not so distant future?