Using TDK DVD+R with Plextor 708A

I recently bought some standard TDK 4x media and burned a couple of backups using the new Plextor. The Plextor tries to burn the TDK at 8x whereas the Fuji-film indicates 4x. although the Plextor says it is burning at 8X indeed it takes three times as long for the burn as it did with fuji-film meda. These two discs seem to now have audio dropouts when played on my standalone
DVD player. any ideas?