Misfires on #5 and #7

It could be the intake manifold has vacuum leaks right near or between #5 & #7 cyl. take it back to who ever did the gasket.

check compression make sure 5and7 are no mix up sometime mechanic get in a herry and mix those two wire it 350 chev engine

replace spyder fuel injectors ,will cost about 800 dollars; your engine light will then go out. This happened at about 125000 miles. It took another 30000 to finally fix the problems.