Is it my knock Sensor? '90 90Q 20V

[David Thoresen]

Well I have replaced the O2 Sensor, changed the oil Castrol Syntech
(5w50)& Filter (Mahle), replaced the Air filter (K&N), replaced the Dist
Rotor and Cap.. I still have the lag at 4000 RPM but kicks back in a
4500 rpm...  I also have a slight rough idle after the engine is warm. I
also am noticing a weird noise (Like paper being torn) at 2900 rpm...
only lasting a moment.

Ok so are the knock sensors easy to get to?  How much are they?  Would
they help me pass my emmisions if I were to get new ones?  Should I try
some injector cleaner first?  (Techron or Guaranteed to Pass?)

Also I am looking at replacing the plugs with Bosch Platinum 4s but the
ones specified at carquest are the wide diameter version and wont go
down the "tube"  Does anyone know the right part # for the ones I need?

Thank you all for your help!

David
1990 90Q 20V 163K Miles