1994 Volvo 940 Oil leak

I have a 1994 Volvo 940 Turbo. Recently had the ignition coil, dist cap, ignition rotor & high pressure fuel pump replaced. A week later drove car to work and noticed an "burning oil smell" when car stopped. On the way home the oil light flickered on & off, so pulled over and put in almost 5 quarts oil. Next day drove it and the oil light came on again- checked the oil and it was empty! Checked the oil pan plug and filter and both look fine - oil is all over the undercarriage and on the engine block but I cannot figure out where the oil is leaking.