Hi i have a 1987 toyota 4 wheel drive 180,000 mile 5 speed. I need help the truck backfire especially when i put in the clutch and going downhill. Also i have noticed that the vacume control valve has one tube missing and when i plug that tube in the engine dies and when i take it off the engine starts. This valve has 4 tubes coming out of it do you think if i replace this valve it will help me i dont want to spend a ton of money if it wont fix it. Thansks Mark