While under my hood Blazer at idle I can not see any vacuum hoses off but I can here a large vacuum leak and when I take the top of the air filter housing off it gets louder. Could it be my T B I gasket, and if so how do I check it and also how hard are they to replace?
Yes it could be the gasket. As far as checking it, make sure it isn't broken or damaged. It is about a three dollar part. If that isn't the issue, check to make sure there are no leaks around the intake manifold.