Took my daughter's beloved V40 to Costco to rotate the tires while the car was home for Christmas, and along the way floored it on a freeway entrance ramp just to see if all was well. Alas, it stuttered, sputtered, and hesitated abysmally.

Got a misfire on cylinder 2 code, so I replaced that coil when I replaced the Champion RC8PYp4 plugs that had 24k on them. Retested, but still the hesitation under hard acceleration, especially from 50 or 60 mph. This time I got a misfire on #3 code. The new coil serves plugs 2 and 3, so I took it to the shop.

They spent all day testing, replacing plugs (with NGK) wires, coils, but kept getting new diagnostic trouble codes that pointed to Mass Air Sensor, Manifold Pressure Sensor, Fuel Pressure Regulator, but none of those parts were indicated consistently. They took the new stuff off, cursed, and gave me the car back for free--partially because my daughter is leaving tomorrow to drive 2 days back to her home. The car does fine under normal driving and gets 28-32 mpg on long hiway trips. (That's the good news.)

So, what to do next? Vacuum leaks? Fuel pump or regulator or filter (which I've been meaning to replace)?

Thanks in advance.
Michael