if you havent got enough air going into the system it will suck best way to find out is remove the vent stack above the tee then flush it
if it dosnt suck you have cured it if it does then its between the tee and the toilet then its either remove the toilet or remove the tee and use a pig tail on a rod to check for any crap up to the pan
however with some pans it can be inside of the pan
my advice if working well, leave it alone a little extra suction is nothing as long as it sucks it all down and water returns to norminal level an 1" or 2" above the bottom of the rear pan