Yes it will effect it accross the rev range, and maybe run a bit hotter than usual, but not enough to notice and can cause the carbs to be slow to settle.
Who did the Ivanising?
Not too unusal for carbs not to be fitted incorrectly and have the inlet manifolds fold in when the carbs are being refitted.
Check to see if the vacuum vent pipes for the diaphrams are clear, there are two, under the tank on the top of the carbs between 1 & 2 and 3 & 4. There is a a little mesh type filter inside the fat tube part and if restricted, could cause the diagrapms to be slow to drop as it would not be able to equalise the air quick enough, although this would also make it slow to respond to the throttle.
If the AIS is still fitted try blanking off the connection to the air box.