Should TP be completely wiped prior to flash?

[reigndropz]

I've been flashing many different ROM's but I'd like to know if we should be completely wiping it first as it appears it doesnt erase everything.

I've been playing with the 1x/EVDO settings and tried forcing it to roam. While it was still set to 1x, I flashed again and when the ROM came up, it was still set to 1X so it didnt revert everything back to its old settings. My main reason to keep flashing is because I'm trying to find the best battery life in these custom roms.

That being said, it seems possible that there are old system settings still left on the TP even after a flash. So should I do a complete wip firsst and THEN flash? If so, how? Thanks