Is this the motion sensor you have? If so, I got one a couple of weeks ago and it works really well with IFTTT (triggers IFTTT pretty quickly)… when it works*. Try just triggering a notification instead of your lights. That would at least tell you help you figure out whether the slow down is in the trigger or the action.

I have Phillips Hue lights and I haven’t seen any significant delays through either IFTTT or Stringify to get them turned on.

.* IFTTT’s Smart Life stuff stopped working for me a few days ago and is now at least triggering again.