I was given a Plasma gun with flamer via some quest, sorry don't remember which one, but anyway when I went for it's modifications it showed a bunch of modifications, but when I went to select that modification it said I didn't have the correct requirement which was Science 3 in which I have level 4. Are there just some modifications for the Plasma gun/rifle that you can't modify even though it shows them in the list? Thanks.

Check and see if you have the materials those energy weapons take a lot more components to make there might be mpre things you need but cant see them try scrolling down with right stick (console)

be sure to scroll down to see the full list of requirements. modding electric weapons require a lot more materials than guns.

Thanks, I'll try the scroll down with right stick.

The flamer mods on a plasma gun tend to be a "dump expensive ammo downrange" button in practice.

I use one very effectively as a close range automatic - bonus free nuclear material in every pile of green goo.