I have been working on vocals for a year or so now... I think I have a pretty good sound as far as you would judge tech death metal vocals... But I still have a few problems

Sustain and Endurance... I can pull off some wicked lows(nile) and great gritty mids(decapitated style). but it really doesnt matter much If I can only growl for 4 or 5 seconds straight right? also I get feeling like Ive been eating red hot, salty, razor blades after about only a half an hour of growling. Is there any special technique changes I should make, or is it just about putting more time into practice and endurance training?

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With vocals as with any instrument, if you don't have the "right" technique from the start you might get decent for a while and, in this particular case, wind up as a wheezing piece of sadness. With a mucus-popping voice.
As far as I can see, the techniques that's been used by classical singers for ages is exactly what we need in metal too, death or otherwise. The most basic thing is to direct the pressure of the air in your lungs in a controlled fashion in the right direction.
About four inches below your navel, there is a muscle called pyramidalis. Just place your hand at it, inhale by letting your jaw and whole body just sag (most notably, your Adam's apple should fall down a bit) and then straighten up, and tense the pyramidalis upwards. This is hard and takes a lot of practice, preferably with a good teacher, but it's worth the effort. Eventually you should be able to give pressure to the lungs from all around your waist. Make sure you're not tensing your shoulders, chest or, even more important, your throat. Note, "connecting the support", as we call it in Swedish, doesn't mean you let out the air - you just make yourself ready to.
The real trick now is to only - ONLY - use your vocal cords to form tones and sounds; they're not muscles designed to do heavy work and if you push them you'll hurt them; and growling is pretty much the equivalent of lifting a medium-sized triceratops. All the force should come from pushing from pyramidalis.

A couple of good exercises to find and take control of the support:
Place your hand on the pyramidalis, then breathe in and out as I talked about above, trying to "hit the bottom". When you're doing it right, it will actually feel like your lungs is situated right below your hand.

Imitate a helicopter with your lips. Breathe in, connect the support, relax your lips and then imitate a helicopter using a tight, controlled airstream. This takes quite some training and experimentation, but is a great way to learn control your own air circulation. Which is, after all, pretty much what singing is all about!

If you're interested there's tons of more exercises and techniques I'd be happy to share.

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thanks man... but what did you mean by the helicopter part?

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You know, that lipflapping thing horses do when they're feeling relaxed... you feel like an utter pillock, but once you can do it for a couple of minutes, you know you're getting somewhere.

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lol, I see

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oh god i can only do that for like 2 seconds.

Keep at it, it's a great way of learning how to control your airstream; try pouting your lips a bit. See, what's technically right doesn't always feel the same way for everyone. When my teacher says "There, you got a real good resonance", which means that the tone is reverberating in the area around the nose instead of in it, I get "the feel" in my throat.
However, you know that when you can imitate a relaxing horse for a prolonged period of time, you are getting a grip on your lung capacity. What a world we live in.

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i think I maxed that out at like 20 seconds today.

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i got like 13 seconds.

but i also have bad lungs.

second hand smoke asthma my crack smoking mother blessed me with when i was a wee little one.

oh snap 37 seconds, but i closed off the air sort of with my tongue like i do when i do gutturals.

BWAHAHAHAHAHA!!!!!
sorry dude... lol

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