It seems variable “hourwage” (link) from IPUMS-CPS comes from PRERNHLY from CPS data. And PRERNHLY has its allocation flag PRHERNAL,presenting whether PRERNHLY is allocated or not (whether hourwage is imputed or not). However I coud not find variable from IPUMS-CPS corresponding to PRHERNAL. I found quality flag for hourwage, qhourwag (link), but it is available only 4 years.
So I wonder if there are any flag for imputed hourly wages since 1990?
It appears that, as you have identified, there is a viable QHOURWAGE-like variable in the raw CPS microdata available through NBER or the Census Bureau’s FTP site. However, it seems that this flag has not consistently existed between 1990 and the more modern data files. IPUMS CPS is currently looking into the viability of an integrated QHOURWAGE across these years. In the meantime, you can certainly merge the PRHERNAL variable from the raw CPS microdata onto your IPUMS CPS extracts for the samples where it is available. You can use the household-level linking variables available in both IPUMS CPS and the raw CPS files and then link individuals within those households based on person order within the household.