when i put mine in my 01 GT it got louder, deeper, and my MPG was the same/less. same DP as the one u described. not much power increase but prly cuz im moving less air than a S/C car.
It would be more noticeable if you had an HV3 w/ a tune.
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