question

This should work:

 $desiredmodels = "HP Color LaserJet 2605","HP LaserJet 3050 AIO","SL-K4350LX"
 $OutputDirectory = "c:\junk\"
 [array]$Downloads = @()
    
 $x=Invoke-WebRequest http://ftp.ext.hp.com//pub/networking/software/pfirmware/pfirmware.glf
    
 $inaprinter = $false
 $info= @{}
    
 ForEach ($l in ($x.content -split ("`r`n"))) {
     ForEach-Object{
         if ($l.Trim().Length -lt 1){
             Continue                    # skip empty lines
         }
         if ($l.substring(0,2) -eq ";;"){
             # do nothing, it's just a comment
             Continue
         }
            
         if ($l.substring(0,1) -eq "["){ # the start of a new printer data set
             if ($inaprinter -and $info['download'] -eq $true){  # if there's a completed record, save it
                 $Downloads += [PSCustomObject]$info
             }
             $inaprinter = $true
             $info.clear()
             $info['download'] = $false
             Continue                        # not interested in the name, just the fact that it's the beginning
         }
         $l = $l -replace " \t+="," ="            # some data sets place tabs immediately before the '='! Remove them.
         [array]$p = $l -split " = "
         if ($p.count -ne 2){        # only interested in lines like X = Y
             Continue
         }
         switch ($p[0]) {
             "SupportedModels" {
                 [array]$models = $p[1].split(";",[System.StringSplitOptions]::RemoveEmptyEntries)
                 if ($models.count -gt 0){
                     ForEach ($model in $models){
                         if ($desiredmodels -contains $model){
                             $info['download'] = $true
                         }
                     }
                 }
                 break
             }
             "Path" {$info[$p[0]] = $p[1]; break}
             "Name" {$info[$p[0]] = $p[1]; break}
         }
     }
 }
 if ($inaprinter -and $info['download'] -eq $true){  # in case there's pending record
     $Downloads += [PSCustomObject]$info
 }
 $Downloads |
     ForEach-Object{
         Invoke-WebRequest -Uri $_.Path -OutFile "$OutputDirectory$($_.Name)"
     }