This air quantity estimation apparatus inputs an output quantity Vafm of an air flowmeter 61 disposed in an intake passage upstream of a compressor 91a to an AFM inverse model M1 to thereby estimate the flow rate mcmi of air actually flowing into the compressor, which flow rate has been compensated for detection delay. The housing comprises a polymer material that does not deform when exposed to temperatures of at least 210\xb0 C. A collar member is supported by the pump housing. The test components may then be measured in order to determine the quality of the holes created by the lift-off process.