Thought I had a blowing gasket over No. 6 and I wanted to replace the turbo so did it all at once. When we took the turbo off, the stud came out when we indid the nut (still attached to the nut). I got a garage over the road to take it out for me. They asked if i wanted them to do the rest (I bought the 12 new studs) and sure enough number 1 had a rotten stud aswell!
mine was running fine, no squeeling, but I read a thread about it and just had a feel. I could get to the rear-most stud and gave it a wiggle, thing just about fell out! Booked it in at Rod's and he said 4 were busted.
Sorry m8 I am not, gasket is 60-80 from Nissan and the studs and nuts are something stupid like 3.5 for a stud and 1.2 for a nut
Obviously you can buy some 10X1mm studs and nuts far cheaper else where but the gaskets a bugger. I have changed mine 4 times all in all with different builds and problems with the O/E manifold .... so there you go a stupid amount of money in exhaust manifold gaskets alone