reinhardt02

first off, i have a bone stock 02 z28 w/ 30k miles on it. m6. catback exhaust w/ some kinda glasspack in place of stock muffler (looks like an aftermarket deal, not some redneck butchered ****) and edelbrock shorty headers. i just bought the car a few monthes ago as is.

cruising down the interstate yesterday about 80 mph a 02ish mustang cobra came up behind me. i was in 6th gear and stepped on it, we hit about 90 and he was tight on me. i downshifted to 4th and steady walked away from him, w/ the a/c on! lol. at around 130 mph and approx 5800 rpm i attempted to shift into 5th gear. it gave me a grinding noise and didnt go into gear. did i do something wrong here? is something broken? is this a common issue? what is gonna fix this?

also, driving down the road at around 70 i heard a quiet whirling kinda noise coming from passenger floorboard area (i think). when i left off the throttle it went away. i drove 60 miles one way steady w/ windows down and t-tops out and didnt hear the sound. on the ride home i had t-tops in and windows up and heard this noise. havent crawled under the car yet to look around, so i have no ideas. anyone have any ideas?

and another thing.... i filled the car up before i left for my trip, and filled up again when i got back. i drove 125 miles and used 5 gallons of gas. i drove 100 miles on interstate w/ no traffic at 70 mph approx, had one burst of 80-130, otherwise gentle driving. drove 25 miles around town when i got to where i was going easy-like. the window sticker for the car called out 29 mpg highway. so my question is: is 25 mpg a good overall mileage for the trip?

thanks for the help ya'll

ben