1996 Toyota Tacoma spark knock

The truck has a chronic spark knock most noticeable
at low speeds and in 2nd and 3rd gear. Looking at
manuals and online with Mitchell and Alldata, I cannot
find a clear reference to adjustment of timiing. Hayes
notes that the distributor can be "turned" to increase/decrease time but I cannot locate the bolt
that would allow the distributor to be "turned". Does the timing have to be programed through the
ECM if adjustment is needed? Or is there another
problem that could be causing the knock such as
the knock sensor. As an aside, the engine seems to be down on power as well. All of this came about after having to have a head gasket replaced which
meant having to have a new head and valve train rebuilt. Thanks for the help.