20mV seems far too low, the transistor shouldn't make a lot of difference to it. If you add the other inductor it will introduce other resonances in the circuit that could result in the instability you see.
The reason I asked about the probe is because at ~100MHz even a small error in probe calibration will show as a large voltage error. Have you followed the probe calibration procedure and adjusted its compensation capacitor according its instructions. Normally you use the 'scopes internal calibrator output to monitor a square wave and adjust the probe to eliminate under and overshoot.
Brian.