I have a 510, a KR808D1 and an eGo (used with my 510 carts, cartos, Mega atty/cart and the tank system). Of all those, I still find my KR808D1 w/carto provides the best TH and flavor of them all. The eGo tank is great in convenience, but the vape is just too cool and the flavor not as strong (good, just not strong and I'm a flavor hog - order all my juices 2x). If you're not willing to switch to the KR808D1, then my suggestions are pretty much the same as others -
* slow, light draws (not like the fast, hard draw you would take on an analog). I mention this b/c (sadly I'm a slow learner) and it took me a good week to figure this out.
* try adding the PGA. I hear that really kicks the TH up a bit
* try using a pass through. I love my 808 batteries, but on a PT, the flavor and TH are even better
* try a LR atty. I didn't notice a difference, but others swear it works wonders - warmer, better TH and more flavor. I just find dripping too much of a pain, especially for any negligible difference (but I am going to try the LR atty with my eGoT and see what happens)
* Increase the nic level. I generally vape 12 or 6mg. I have a few bottles of 18mg and samples with 24 and WOW - almost too much TH with the 24 mg (although that won't do anything for warmth).
Can't speak to mods, since I don't own one (although am considering an Old Goat....)