The FRPP T-body is way too massive for a NA car. The FRPP Manifold is also huge. You're sacrificing a grip of low-mid power for virtually no top end gain. You have huge air volume and low air velocity, and no cubic inch to back it up. That setup needs a blower huffing into it to make use of it.
Regardless, the T-body would be a possible idle issue component. The movement of a t-body that large would have to be extremely small at idle and have huge effects if the movement weren't tight enough. Abormalities in TPS voltage alone would cause significant idle hunting. Particularly if having alternator issues as well.
I have the FRPP twin 62mm TB on my 2010 auto ( with small roush M90 blower). The idle is superb, doesn't budge. The FRPP twin 62mm TB is made by acufab, same outfit that makes the oem twin 55mm tb. The FRPP twin 62mm TB won't buy you anything on a NA car, but it won't screw up the idle either.