My 91 RC has a bad venting problem, in that when you pull a trailer up hills after a lot of driving (pressure building in tank) it starts bucking and losing power from lack of fuel. I have replaced all the fuel lines and filter, put two new fuel caps on it, checked the filler neck, and it still won't vent. After an hour of driving, taking the cap off makes you feel like you're going to get sucked into the tank. I can leave the cap loose, but I am not satisfied with a "quick" fix like that, I want the "proper" fix.
Also, when it's running there is a "whine" coming from the fuel pump, like a high-pitch motor whine. Not really loud, but noticeable. I have put other pumps on it and they all seem to sound that way. Is that normal for these early-FI trucks?
Any help is appreciated!