I've got a 750SXI Pro I got second hand and don't know too much about but it seems to have a lot done to it. R&D Head Factory pipe dry pipe Skat trak intake scoop Jet unit appears to be modified as well and has something written on it about 82mm reduction After a bit of work its been running well, but the other day it suddenly got louder and exhaust water box getting sizzling hot. I suspect no water going through the exhaust. Cooling system appears to be modified and has two water supplies from the jet unit (i believe they only have one standard). First feed goes to the engine block, then from the top of the head there is two lines for the tell tales with a third going to the dry pipe which then exits from the dry pipe and goes out a third tell tale. The second feed goes to the exhaust manifold, i'm not quite sure how this works but I assume it injects water into the exhaust manifold which goes through the exhaust, the waterbox and out with the exhaust gases, this keeps the exhaust cool and also quietens the engine. I have blown air down all the cooling lines and none appear blocked. To me these two cooling feeds should be seperate from each other, but when I blow air up the feed for the exhaust manifold I am getting air out of the two tell tales from the cylinder head and i'm not sure how its getting there. To me they shoud be seperate?