i have a 1990 ls400 and the iac went out.. when the mechanic pulled it out the part number on the unit was 22270-50010. of course this thing is $700 brand new. so i went to the used parts dealer and they give a unit that listed for 90-96 and was a little bigger and the part number is 22270-50020. it will fit . wondering what should i do. install it? or keep looking for the original one? the plug is the same.
thanks

 

According to the workshop manual both part #s are listed for the 1990. Fit it and see if it works, remember to replace the gasket ( part # 22278-50010 or 22278-50011) this may be for the 2 types of the IAC.