You will not get any reply from King, he is busy now and your question was asked million times already. Read the posts, man.
But since I have decided to write reply, I will explain. Open mission.lvl in UltraEdit 32 and search for tat1, then search for SIDE until you get to imp.lvl section and repleace imp_fly_tiefighter with imp_fly_tiebomber (add 00 if needed). Open tat1.lvl and repleace imp_fly_tiefighter with imp_fly_tiebomber.
Make sure you back up your mission.lvl and tat1.lvl before doing this.
If you want to add tiebomber with tiefighter then you have to replace something else in mission.lvl such as darthvader.