Knock in my engine? Or pulley noise? Car:2004 Mustang gt miles:115k miles?

My car has had a knock noise from the day i bought it should have been a red flag but i test drove it and it drove fine. Recently did an oil change and my timing chain guide broke and clogged up my oil screen so i had new timing chains guides and chains along with new tensioner and water pump as well as new seals and gaskets replaced at my mechanics shop when i heard it start again the engine bay was a lot quieter than before but the noise has come back my mechanic told me he found no metal shavings in my oil pan and that my cams and valves looked fine, the noise is present at cold start and warm up but can be heard clearer when i have it in drive or reverse.Transmission shifts fine also. Any suggestions on wha it could be? I also changed the spark plugs with ford oem plugs about a month ago i haven't changed the coils though.

Could be pistons or wrist pins.

If there are no misfires why would you even think you needed coils? You may just have piston slap with that many miles. If the oil pump was plugged up with debris from the tensioners breaking you may have some bearing problems but you'd need to take the oil pan off and check the beraring clearance.

Well, it's not the timing chain and guides. Could be piston slap and rebuilding the engine would fix that. Could be a worn out connecting rod bearing. Pull the oil pan and shake the rods to see which one wanders on the crankshaft or has too much side clearance. The bearing will need replacing and the crankshaft will need to be reground.