Engine misfire noise

[Ghiser]

I have a vg30e engine its a v6 3.0L

I know the title to this forum is odd but I have been struggling with my 1990 Nissan hardbody. A couple of months back i had replaced the valve cover gasket on my truck because I noticed it was leaking oil from the valve cover. It was a multi day process(because it was my first doing something of that magnitude) but after i finished i noticed a misfire sound I suspected it was a vacuum leak so I ran a vacuum test, and there were small leaks but nothing that will cause such a grand sound. P.S i forgot to mention i did reuse the intake and egr gasket like an idiot. I asked a mechanic he told me to replace those gaskets I did but it’s still making that noise. Since I replaced the valve cover gaskets i had to remove the distributor but i didnt mark where it was originally. An added bonus when I removed the distributor i left the distributor in my garage for a couple of days. I read the code and the ecu was showing me a knock sensor code.

I know those thread is a jumbled mess but I completely stumped and need some guidance or help.