My engine squeals loudly on start up. It gets less loud as the engine warms up. Sometimes, noise goes entirely away. I took off the T-belt, and the drive belt. Checked each pulley, roller, and tensioner, no problem. Checked A/C compressor, water pump, alternator, and P/S, all well. Replaced the two belts, and put back. Noise still there. It appears to be generating in valve train area. I listened with st. scope all around the engine, and again, no one particular area sticks out. I'm using conventional 10W 30 grade oil. Should I just replace the serpentine belt tensioner. I'm out of ideas...