I often load a match and experience frame rate lag spikes.
I've realized this only happens when I load someones textures or flames/items.
If I've already dl'd their active inventory there's no lag.

I don't know if there is some common fix to this or It happens to everyone sometimes. Help is appreciated

yeah, it have happened to me before
quite often, actually
i suggest for u to do this:
esc>setup>options>turn effects to whether only on replays or always off