the knock sensor isnt hard to get to, just pull the ic off. torque the sensor to spec, it's the easiest of the possible issues... and cyl 1 is furthest from the knock sensor. remember how detonation can occur- poor fuel quality, too much timing, too little fuel, poor compression, hot charge temps. your knock correction is massive, more than just the typical pesky knock. a false knock- like loose bolt on the engine somewhere could cause this. or poor engine grounds too.... check your engine grounds, there should be ground straps attaching to the left and right frame rail and to each head.