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Help with sealing drafty modern vinyl windows

Now that it's turned cold outside, I've noticed that near my windows is quite drafty. Considering I live in a pretty new raised ranch with modern vinyl insulated windows, I was surprised that it was so noticeable, so I decided to take a look.

After battling the trim for about an hour, I discovered that there is only a minimal amount of fiberglass insulation packed tightly between the window and the rough opening. In some places there is none.

My initial thought is to pull out all the fiberglass and spray some minimally expanding foam into the gap, but since the window isn't centered in the opening, I will just have to use caulk on one side since there isn't a space for the foam.

Since there is housewrap stapled to the rough opening, am I supposed to shoot the foam in between the house wrap and the window frame? What about caulk, should the caulk seal the housewrap to the window frame, or should I be trimming the Tyvek back flush with the window frame, then caulking the window to the rough opening (the wood)? Should I finish up with some foil tape as an added barrier?

The other problem is that the trim work (jam extensions and sill) was assembled as a unit, screwed together, then nailed into the opening on all 4 sides. Even stranger is that the trim "unit" is actually about 2" narrower than the rough opening. As a result, I pretty much had to destroy it to get it out. Since the walls are 2X6, am I just supposed to make jam extensions out of 1" stock to come flush with the wall on the top and sides, nail them into the rough opening and then trim out as desired?

Any help would be really appreciated...

Re: Help with sealing drafty modern vinyl windows

I am not really qualified to answer these questions, but maybe my reply will spur someone with the knowhow to respond.

I built my own 600 sq.ft. addition in AZ using new construction vinyl dual-pane single-hungs. Since I did it myself, my rough openings were purposely close-fitting and square, and as such I have no room for expanding insulation. The lowest temp we have gotten this year is 28 degrees F, so compared to Maine temps, any drafts I have felt are going to be minimal. Still I felt a very small amount of air movement at my son's new window. From my understanding - & this is how I did it - at the rough openings, the Housewrap comes all the way into the loving space & should be attached to the studs behind the drywall, so all window & door insulation should be btw. the Housewrap & the window/door. I still don't have the window trim up at this point - some stuff is slow-going, but that is probably how I was able to detect the small draft. I will caulk the window to the Tyvek before I put all the trim in sometime soon. Now by comparison, my exterior door opening was roughed very large to compensate for my inexperience with doors, and I needed to use alot of foam there. Since the door jamb is the full width of the framing, I have drywalled right up to the jambs & have noticed no drafts.
I would say to caulk the smaller gaps btw the Tyvek & the window & carefully foam the larger gaps btw the Tyvek & window. I would make stopping air movement the 1st priority & insulating the second, reverse of what the builder's subs did.

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