I removed all manifold bolts and connecting down pipes on my VR today with no problems.
Soaked them in wd40 and left for ten mins, then cracked them off with GOOD snap on sockets, with more than a meter of leverage.
Probably worth noting too that the engine hasnt ran in months, so the bolts were cold and hadnt heated up in a while to sheer.
I wouldnt advise doing it if the engine has ran in the past day or two (to allow for cooling in evening temps etc to allowe best chance of getting them off)