That would be some airgun. I've got a Chinese monster-rifle that can put a .177 pellet through a wall, but I wouldn't trust it on a coyote. To me, something more powerful is in order in this case. Maybe a Mosin Nagant (for about the same price as a good airgun)? I would be interested in hearing your reasons for wanting to use an airgun for this. Have you considered a crossbow? They have the range and the power, although I'd still want a firearm (at least pistol) just in case and to humanely finish off a wounded animal.
The RWS 350P in .22 produces 1000 fps at the muzzle, $340 http://www.airgunsofarizona.com/rws.html. Not what I would go after coyote with, though. Get a nice AR 15 in 5.56, like this one from Del-Ton at $780 http://www.del-ton.com/DTI_20_Rifle_p/rfth20f-0.htm and do the job right.
I looked into air for a while until I found out they were as loud as a .22. Not much help for the neighbor that is anti everything I believe in. 45 Caliber Big Bore Pellet Rifles, High Powered Air Guns for Hunting at the Best Sales Prices notice it says loud as hell. AirForce Texan Big Bore Air Rifle. Air rifles - PyramydAir.com either one will do job, but I think your looking for stealth.
That's the crazy thing I found out too. I was all excited to hear you could get larger air guns, not so much when I found out how loud they are
I use a Gamo Silent Cat and have had good luck. Punched holes through rabbit heads many times before. Another good option is the Hatsan 135QE. Shoots a .30 cal at 550 fps. There are 2 main air rifle features that put animals on the dirt; power and speed. A .177 pellet going 1200 fps will knock out a yote easy, but so will a .30 pellet going 550. Get an accurate one too. You want accuracy so you can put a pellet to the bottom or left or bottom right of the ear, depending on the side. As for the power plant, it depends. A break barrel will put animals on the ground but will be a little louder and will lose velocity faster. A PCP airgun will put animals on the ground, be quieter, and lose velocity faster but you have to haul around a air tank if you want to do lots of shooting.
