Ok, I have an 1989 F150 XLT Lariat 5.0L 302. The engine light is on and stays on until I put my foot on the gas and then the light goes off, and then when I let off it goes back on. Now I have no idea what the problem is. My dad says it is a vacuum leak in between this t-spilt, by the airconditioning under the hood. I took it to the motorcraft store and they said it is a "fact valve"?? idk. I just want the light off cause it is driving me insane seein the light go on and off. So if anyone knows what it could be could you please let me know.

Thanks.