Exhaust leak??

[xpinoyxmk]

So i've been having a lean issue with my car for about a month now and i think i found the problem.

Problem:
-Studs on turbo mani loosened and 2 top bolts on downpipe are seized up

Issues are:
-Afr is lean at first when driving(not in boost), like 16-17 afr but drops after about 10 sec to mid 14s
-Car bucks when its in the condition above till it stabilizes in the 14s
-When full throttle, seems laggy, sloppy spool, afr is the 14 range at full boost

My setup is:
Ka-t, solid 180 across all 4
Stock bottom end
arp head studs and felpro headgasket
s14 t28, 8lbs, no shaft play
370cc inj, were cleaned and tested by DW
Walbro, confirmed that its good
Isis fpr, set at 43, confirmed that its good
Nistune, little tune i threw on there

So are those issues caused by that problem?

Before my car ran perfect, went for a cruise, did 1 run with an evo(2-3 pull), stopped at a gas station, let it cool down for about 3-5 minutes, shut her off, went to start her back about and it ran like crap. Thankfully had my laptop and got it running decent enough to get home.

Now i have to figure out how to get those 2 bolts on the downpipe off...

Any help is appreciated.