Since last fall my mileage dropped I was getting 30-34 (it's all in the foot) at the tank and slightly higher on the computer. Now I am getting 22-25 at the tank and 24-27 on the computer. I had the new bosch 3's in last spring and when the mileage started going down I tried some Bosch 4's from Jon. Mileage stayed about the same and a little less. So after I got the 3's back from Jon to check, they were ok I put them back in and mileage was about what I was getting when i changed them out . By that time it was winter so parked the car til spring. So far same. Was getting what I thought was a lot of pressure from the fuel tank. Thought I might have a plugged or bad Evap charcoal cannister . well I took a line off up the engine (LT1) and it was plugged. I thought it was rubber as it was an original hose "93. Tried to blow on the line going back but was not getting any air through it. Saturday I took the plastic cover off that protects the cannister in the rear and the hoses are plugged going to the front and the cannister was leaking out the little pieces of charcoal that I thought was reuuber. Have a new cannister on order. Need to see how easy it is to pull that line out to clean as I don't think I can just do it with air. Since they are little pcs. if I could stand the plastic pipe up I think thyey would fall out on there own. Any idea's on that. Also replacing that bypass check that goes from the canister to the fuel tank.