Hole in exhaust manifold

[air-cooled or diesel]

I'd pull the manifold and weld up the hole.

as long as you dont set anything on fire you can clean/weld from underneath; take precautions, mostly like welding an exhaust only near engine. weld in a circle get penetration to base metal and close circle just becareful not to get weld so hot you blow thru, if you have to pause,,doesnt have to be perfectly clean, may help, but will still rust.

[burn_your_money]

Personally I would remove the turbo, then remove the exhaust manifold. I wouldn't touch the intake manifold unless you needed to (rounded off exhaust nut). Use new hardware when you put the manifold back on. I always use the copper nuts for the exhaust manifold. Don't forget the washers. I would reuse the turbo bolts unless you see reason not to once they are removed.

Remove oil feed line at turbo
Remove lower part of oil drain line to oil pan 24mm I think
Remove single bolt that holds the oil drain line to the back of the block somewhere near the middle of the pipe (may not apply in your case)
Remove intake pipes
remove bolts from downpipe to turbo unless the mk2 toilet bowl style downpipe is used, then just unhook the C clamp things
from below remove the 4 12mm 12pt bolts that hold the turbo to the exhaust manifold
remove turbo from car
remove 8 12mm nuts that hold exhaust manifold on.

You may want to drill and tap the new exhaust manifold and put a plug in it if you ever plan on putting in an EGT sensor so you don't have to go through all this again.

[air-cooled or diesel]

my fault i failed to see its a td, dont weld near turbo, tap and plug sounds easy and good,, or it has to come off to weld, or away from turbo,

[homerj1]

Thanks for all the advice, guys!

 I just haven't had a chance and probably the courage to give this a go ... yet.
Will try to see if the turbo off first method will work ( assuming I can access all the bolts? as the turbo is a T3)- as I think when the turbo out - all the exh. manifold bolts are easily assessable?

But first have to deal with the oil filter flange gasket leak that is leaving black spots all over town....