Insulation, Radiant and Vapor Barriers - cold 2nd floor

Let me start by saying I have the only 2nd floor that defies physics. My 2nd floor is drastically colder than my 1st floor. I live in the north east and just put in an additional R30 insulation .in my attic to my R19 already there-still cold up there
I have walls that follow the roof line aprox 4 feet w/ R 19 in them not so much of a cadereal ceiling as it levels out under a hip roof.
I also have soffits that are mainly open.
vinyl soffit panels cover the soffits with about 6 panels that have holes in them.
I cut a hole in the drywall and could touch the vinyl and feel the cold air.
I am planing to reside the house(a semi attached) using tyvek and insulation panels should I close in the soffits?
I was thinking about 1/2 ply or the insulation panels to close them in - leaving the same amount of open panels .
windows are all new. any input on covering the soffits i'm getting mixed reviews from friends

Dont worry your 2nd floor is still following physics. Before you added all that extra insulation did you do any serious airsealing of attic bypasses and penetrations? Im not talking about weatherstripping doors windows etc. Manytimes just adding more fiberglass isnt enough to do the trick. Ditto that for adding more ventilation. If the sloped ceilings you have dont have rafter vents or something to channel the air that goes up them the air wafting up is degrading the R value of your R19. If you have good access theres things you can do to block off the air from the batts while still keeping good ventilation. Id keep the soffits open and work with them in solving your problems.
Before you do all the expensive and hard residing work theres alot of things you can do cheaply that might well solve your problems. Where the sloped ceilings meet the wall--do you have a small side attic space or storage area behind it or kneewall? Are your walls insulated? Also you should have R49 up in the attic not R38 but adding more now might have diminishing value.

Wouldn't be anything much simpler like an unbalanced forced air delivery, would it?

Yep adjusting dampers would be the first thing to do if they are there.

thanks guys 1st theres no dampers just regulated by registers - went through the task of having them all open and taking temps in all the rooms and leaving the colder rooms more open than the warmer ones.
also i used to have only 2 returns one in the main living area 1st fl (an open floor plan) then on in the 2nd floor hallway- when I was in the attic area i added 3 returns 1 in each of the rooms up there they seem to be working fine
the rafters have the vents upto the open attic space.
no acess to attic area w/o cutting into the ceiling again.the side walls are the exterior walls (understand?) no space behind them -if i take down the drywall & insul can touch the sheathing they have R19 in them.
when I was in the attic area I used expanding foam on all of the plumbing vents etc that went through the roof, I also have 2 attic vents up
maybe theres a better way to balance the forced air?