mine did the same thing a couple of months ago. Mine was that vaccum line like pitman said earlier. It has a coupler in it between the pass. shock tower and the firewall. Mine was just pulled apart.
yours did the same thing as mine or the same thing as the OP?
98 GTP Coupe- 180* T-stat, GMPP Front Sway Bar, Dual Aeroforce Interceptor's, TDC FWI, TDC Taylor 10.4's, ZZP SS Plog, ZZP 3" SS catted DP, ZZP MPS W/3.4, AL104's gapped @.055, 3800Perf. PCM