engine problems

this is my first post on here so hello everyone and thanks in advance for any and all help or suggestions.... so fist off im not too familiar with 4runners and not so much with macanics ether, anyways to the point. i just bought this 1991 3.0 4runner with 240xxx plus miles thats having a loss of power. i did learn that there is a loss of compression on the 2 back cylinders which leads me to believe head gaskets however i know the valve cover gaskets need to be replaced too and im having no other symptoms of head gasket. also the fellow before me did some "custom" work on the mass airflow sensor lines and possibly intake??? anyone have any ideas where to start with how to figure this out? i dont want to replace gaskets without need be... thanks again

 

if you don't want to replace the head gaskets, you can try tightening the head bolts a little extra while you have the valve covers off. it might help for a little while for cheap.
i would recommend... if the head gaskets need to be replaced, replace them. it's a fairly simple process, although quite a nuisance. i prefer to go for reliability, but... money is money.