Hi all,
It's my first time posting here and hoping I can get some guidance before I start asking local professionals.

I bought a home in CT 3 years ago and am disappointed with the heating in one zone. The last set of baseboard takes till the end of the boilerís cycle to get warmed up on one side of the house.
Itís a hot water boiler hydroponic system with baseboard (fins). There are 4 zones (1 indirect hot water) (3 living areas)
Boiler is Burnham Oil fired. Main loop in basement starts with 1.5Ē black pipe into expansion tank down center of basement then splitting off to the multiple loop and mono flo zones. There are some check valves in this area but donít recall the placement. The primary loops (front Ĺ of house and back Ĺ of house have their own loops at the split that return to the boiler) supplying the monoflos is 1Ē black pipe coming off the 1.5Ē with multiple mf and regular Tís coming off for each baseboard. The return going into the boiler passes through the circulator pump which is flowing towards the boiler.
The main living area on the main floor (split level ranch) is a mono flo system. The other two are loops for the bedrooms and downstairs.

I think they screwed things up when they designed this system because its my understanding you donít want a long line of radiators on a monoflo system and that last line near the end of the main loop is over 60 of baseboard before it drops back down. (this is the line that is forever cool near the end till the end of the boiler cycle (15 minutes or so).

Thereís part of me that just wants to scrap the whole monoflo system and go with a loop but not sure if itís a wise decision because one side of the loop (series) is almost double the length of baseboard as the other side.

I just feel like this is a very inefficient use of heat. The basement is always toasty because of all the heat running through that main loop but the main floor is slow to warm up at the far ends. Iíve bled all the lines till the valves were dripping so I know its not an issue of an airlock. Iíve also checked all the direction of the monoflos to make sure they were installed correctly and they all seem to be right.

Coming from my old house which was much simpler (1 zone series loop) it always warmed up much quicker and the slantfin was always hot to the touch. This system it seems the heaters just never get that hot.
Technician during last cleaning changed (increased nozzle size) some nozzles sizes on the injectors thinking this would help for some reason but the only thing it seems to have done is use more fuel (maybe in my head but last year was warmest on record and we used same gallons as previous year.)

Iíll try and draw up a diagram of the plumbing tonight and post it tomorrow as Iím sure the description above is somewhat confusing.

To add fuel to the fire, Iím debating on converting to gas from oil soon so will be replacing 25 year old boiler and hot water system. Want to make sure Iím not just wasting $$ on new equipment that runs through a possibly poorly designed heating system.

Any help would be greatly appreciated. Even if itís just guidance on what to look for in choosing a professional.