I have recently had to rearrange my valve lifters in order to tune to an optimal clearance between cams and lifters, which on my Tacoma is 0.15-0.25 mm for the intake and 0.29-0.39 mm for the exhaust valves. I had performed multiple rounds of measurement meticulously and had to order some new lifters as some valves were so much out of the range that none of the existing lifters (which come in different gauges) would close the gap.
But I did it because I had my cylinder heads open and had easy access. My question is, how does an engine that has loose or tight valves manifest the anomaly? What are some of the symptoms by which you'd know that you need to tune your valve clearances?