89 305 engine knock........help

Hi,.
I have a 89 firebird with a 305 tbi..
When I put the gas to the floor some times I hear a litle knock,knock in the engine and then I get a litle puff of smoke out the rear....At the moment this hapens it feels to have no power and then all of a suden it will pick on up and take off as normal with no smoke.
It also gives me a a nice puff when I nail it hard..

I know the valve seals are gone for sure at 108,000 but if I need a set of rings due to the smoke when I nail it could they (the rings) also cause the knocking sound I am hearing when I take off at lights or slow down and speed up rounding corners,,. Just when I first accelrate then it clears out.... Any one had this type of problem??

Thanks for any help..

never had this problem every time my cars develop a konck they dont last long but any way what color is the smoke gery black or blue but yer right the rings can give a knocking sound but make sure the car is timed right look at the plugs and see if they are clean and white or if they are dark and even try a higher octane gas it could be spark knock or your car is loading up with fuel

possible wrist pin (s)
probable thurst bearing and rear cap bearing wear
oil psi is still enough to fill the space when u get it reving sounds like
that's why the knocks becomes unaudible
(it's still there though)