New HVAC

XR 90 probably means 90% efficient as the XR80 is 80% and mid efficiency. You have a builders grade but not bad furnace that is only 8 yrs old and DOES NOT need replacing unless you have $$ burning a hole in your pocket. Any furnace over 90% is high efficient and most can use 1 0r 2 plastic vent pipes even the new ones today. As the builders go with 1 pipe to save $$ but I would not get rid of it.

Depending on whether you live in a wide open house or I hear in TO the row houses are reall close together. If the houses are real close together then the exhaust can hit the next one and recirc back to the intake pipe and the furnace won't run with exhaust coming in. Mostly they don't want to drill another hole and use more pipe so they go 1 pipe. Post some pics of the venting where it exits the house. I doubt you will notice a huge NRG saving and having to pay someone several hundred $$ to redo it will never pay for itself in fuel. Ontario is VERY strict about codes with the TSA or whatever they call it monitoring contractors so I WOULD NOT redo it myself for liability reasons. May need a permit and re-inspection if you alter the venting as that is legal venting not DIY stuff.