Outwardly upset motorists due to taking the lane are so rare as to be a non issue. I very often use the full lane on 40-45mph multilane roads. Drivers see me well into the lane well in advance and those who are capable of thinking ahead merge left to pass. Those who don't find it a bit harder to get up to speed when a gap in the left lane opens up.
My experience is that if not taking a narrow lane and instead riding far right will upset more motorists as they can't tell early it is not possible to pass safety without using the adjacent lane, but by that time it is too late for an easy merge left even for those who can think ahead.
As to the OPs experiment, it needs more data points. I have driven slowly in my SUV and gotten honked at on same road I don't get honked at when cycling. But if a honk is 1/10000 drivers you need more test time for each mode to determine if there is a real difference.
As to exhaust - don't stop right behind the exhaust pipe! I typically stop 6' back in the left side of lane (behind driver side), well behind exhaust which is often on the right side of vehicle. Also note if you do filter, all those cars will spew exhaust when accelerating past you which will be worse than idle exhaust.