Greetings all--new to the forum and to the FE.  Subject line pretty much sums up my question.  Given all of the horror stories I've heard and read regarding header fitment on a Thunderbird, I'd really prefer to stick with the stock exhaust manifolds and have a proper 2 1/2" exhaust system with h-pipe built for the car.  BUT-- since so many folks here and elsewhere believe the stock logs are such a choke point--I wonder if they would largely negate the impact of installing an upgraded intake like the RPM and a decent set of heads, even with a free flowing exhaust from the manifolds back?  I'd appreciate any and all insight!