I acquired this 4-runner a month or two back now and I haven't had much time to work on it. When I got it, it was lacking power and needed a new timing belt so I went ahead and replaced it. (Not new to that part) After I replaced it, I still felt like I was lacking a substantial amount of power so I got a compression checker and come to find out I only have 30 psi on cylinder 3. What would you guys recommend me check first? The head gasket? Valves? I would generally start with replacing the head gasket, but I'm new to this car so I'm wondering if there's a known thing that goes wrong like maybe the intake valve or something. Thanks.

 

A cylinder leak-down check is in order.

It will likely reveal a burned exhaust valve in cylinder #3.

 

Probably carbon build up or a burnt valve if your not having any other issues. A leak down test as suggested would help you pin point if it's valve or cylinder related.