You could do just fine on an e-tune, even an OTS tune would probably be OK for an interim period. I'd imagine Shamar has tuned a ton of 16g setups, just log after your tune to make sure it's safe.
I'm in the camp of "if it's a street car you should have a cat", but to each their own I guess. You'll see zero performance gain going catless, just a bit of savings.
Going with the etune and upgrading the oil lines per BNR would leave you about $175 to play with--you'll probably need that anyway for random bits such as hardware, heat wrap, etc.