Any engine codes thrown?
Pull the Coil on plugs to see if the knocking gets worst, if the knocking gets worst then that coil is not the problem, if the knocking stays the same you've found your problem.
You might wanna choose a higher octane of gas just to rule out the gas.
Spark plugs could be fouled as well.
you should post a sound clip, it could be alot of things. hell, i had a 'knocking' noise on start and hard accel after i put the blower on and it turned out to be the cai lightly tapping the passenger side shock tower... so, you could have a bad motor mount, or a spun bearing... its best to post a clip.