"enough backpressure" there's another one of those great automotive myths.. any backpressure is too much. this is why we build free-flowing exhaust systems, to reduce/eliminate backpressure.
if money isn't a big deal, consider a TPI swap, or some other aftermarket multiport efi system. be ready to spend near $3,000 for it tho.
but again, this is like buying a new car.. with what the new vehicle is going to cost you, you can buy a LOT of gas.
when you consider your new vehicle payment..say around $500 a month. plus having to have full coverage auto insurance on a financed vehicle.. this could be anything from $200 to $1000 a month depending on the state on your driving record and insurance co... you can burn a lot of gas for upwards of $1000 a month!!!