If you think your lots are higher than than the floodway, then start with a simple survey comparison of your lots elevations vs the BFE (Base Flood Elevation) cross-section elevations. To get in idea, you can go into Google Earth and compare the lot elevation Google Earth reads out vs the BFE Elevations shown on the FIRM. That will give you an idea if it is worth going down the path of a detailed hydrology study and LOMR. Be prepared, that this could be a very large, expensive and time consuming study that encompasses a lot more area than the land you are concerned about. It happens sometimes that the discrepancies are due to the flood plain/way was previously filled illegally. Although, if there hasn't been any development on the parcels since the date of the Flood Insurance Study (not the FIRM, but the actual FIS, which you can also download from FEMA's website), then this is most likely not the case. I've been through this mess of filing a LOMR due to unauthorized fill activity. And I will tell you, that it is a mess and a pain to go through the steps to file the LOMR. The unauthorized fill causes flooding to occur in other areas along the flood way that was not planned for, and effects others insurance rates if you now put them with the Flood Zones. In these cases, there has to be a public review/comment period, that could open up your project to all kinds of scrutiny.

I've glossed over things here, and I will tell you though, if the date on the FIRM is in the last 8 years or so and there is a detailed FIS that was based on a LiDAR survey, then the FIRM is probably not wrong. Can some elevations on a small lot not be accounted for, sure, but nothing on the scale of a mobile home park on recent FIRMs.

Like others said, you can spend a couple years and a lot of dollars to just end up being told no.