How's it going guys, I've been searching around for topics on my issue and figured I've post one myself regarding code p0301 that's causing my CEL to come on. I've been dealing with is code since last summer, July to be exact, I've replaced fuel injectors, wires, spark plugs, and coil packs all oem and ive noticed that the CEL will go away from about 2/3 weeks then it will re appear. It simply turns on, doesn't flash or anything. The ideal feels fine, no indications of stalling or anything like that.

Would anyone have any other suggestions on what it could be? I've read on other posts it could be a head gasket issue or even the actual cylinder head. Any feed back helps, as I would like to keep my 97 4runner as long as I can. Thank you in advance for any help/info!

Did that include checking all the connector connections and vacuum connector connections?

Verify all connectors you messed with don't have broken tabs. If they do replace those for secure electrical signals. Compression check. Leak down test. That's where I'd start. If all passes you can mess with u.v. dye through the system and see if the dye stains anything using a black light. All in all all 3 tests will run you $150 in supplies assuming you own an air compressor. Shops near me charge $100/hr with a 1 hr minimum...so 50 bucks more you got unlimited ability to repeat all 3 tests at any point on any vehicle....yours, families, and friends.