I have a glowshift fuel pressure gauge on my 2000 24 valve, and it's never read right, but now it reads 15psi when i am on the go pedal cruising down the road. But as soon as i let off it spikes to 30 psi then drops to zero and stays there till i get back on the fuel. Also when i first start the truck it idles at 10 to 15 psi but as it warms up it starts acting up.

Any ideas???

Thank you everyone!!