(2 tracker exhaust fumes leaking

92 tracker Lsi 1.6 8 val 4x4
15 mins into driving I start to smell fumes and I have the top off and all windows down but it is really bad , I hear air leaking like a gasket blew, where do I look for this issue. muffler is bad with holes,
could it be a head gasket blown ?
Also when it's hot! I live in Reno, the car goes into gear really rough but when the outside temps cool it shifts fine, any clues

Well from my experience if the exhaust can make it out of the muffler on the sides or no tail pipe is attached it will come up the sides and blow back in. if you have an uncapped hole in the fire wall and an exhaust leak at the engine it will come in that way. find a local muffler shop and have them check it. If you need a muffler go to a custom exhaust shop and buy one (for cheap) they took off a new car that had custom exhaust done

Check the connection to the exhaust manifold, especially if you have had any exhaust work done recently.