1998 Subaru Forester light throttle hesitation at around 20

Hello my new to me forester much like my previous legacy of the same year but had 180k, has a wierd hesitation on light acceleration around 1800-2200 rpm, feels like it's stuck in the mud, seems much more noticable when engine is cold, but ocassionaly feel it very slightly with a warm engine. I just bought the car and have new plugs and wires yet to put on but feels like either engine goes lean or possibly timing is backing off. I have read that it is possible the knock sensor could be picking up on the piston slap and backing off timing. Do you think this might be the case, my scan tool says 15 deg. Advance at idle, gonna see if it will record as I drive.I was thinking of unbolting knock sensor and tieing it off somewhere to see if it helps, also read about putting a rubber washer between sensor and block? I don't want to unplug it because i'm unsure if it would cause timing to be backed off all the time, does the knock sensor even work in a cold "closed loop" situation, or do you think I should be looking elsewhere, all vaccum lines are looking good egr is working fine, vacuum reads 20 at idle but flutters a bit, i'm hoping tune up will cure this, I replaced pcv, cleaned maf, throttle body and aic valve, tps reads around.5 at idle and 4.5 at full throttle, no codes, other than this runs pretty good, does shake pretty good at 800rpm in gear, enough to rattle door panels, but seems to smooth out as engine warms and idle drops down to around 650-700. Please help this thing is driving me nuts