I just bought a vintage v100 on monday with Wilkinson pickups. It sounds good with distortion but if I play it clean it sounds thin and tinny. Should I buy new pickups or is the problem somewhere else?
What's your amp, pedals and what settings do you use? And which V100 do you have? There's one version with humbuckers that should never sound thin and there's another with P-90s that can sound fairly thin with certain types of amp.
I'm using a peavey envoy 110 40 watt amp with a Zakk Wylde overdrive pedal and i played with the tone knobs and it still sounds thin. It only happens when im using the low gain input on my amp but when my friend puts his epi. Les Paul in my amp with the same settings there's no problem. I have the v100 with the P-90s.
Your friend's Epiphone has humbuckers. Your guitar has P-90s. There's your difference. P-90s are big single coils. When you use distortion they have just enough power to them that they can sound just like very bright humbuckers, but clean they're going to sound more like regular single coils. They're really best with in-between, slightly overdriven tones. That's why your guitar is sounding thinner clean.
If your guitar has a treble bleed capacitor on the volume pot, rolling back the volume won't thicken up the mix much, but if it doesn't it should help out.

Also, get an EQ pedal, it will give you way more control over your tone, much more than a pickup swap. The Danelectro Fish and Chips is $30.