you have hydraulic lifters so no valve adjustment is possible. Either the lifters work or they do not. Clean oil is important. My valve train improved over time.

I dont know if the relay is vital or not-- with mine, the engine stays at the right temp winter and summer although I never get caught up in traffic, since there isnt any here. I've heard that with this engine, the fan clutch, which is electrical, doesnt deploy unless the ac is engaged. I dont know if this is true or not, my fan clutch never seems to work, but as noted, I've never needed it.