car is hard to start, and when i snap the throttle it bogs down really bad and will stall out. if i ease into the throttle it will rev up just fine. it does this cold or hot. swapped out the distributor and coil with used ones. replaced spark plugs and wires. Checked operation of the throttle position sensor and map sensor with voltmeter. Any ideas ? parked my car one day and it just started doing this.