Stock TB is basically 48mm. Opening it up to 50 is reportedly a noticeable improvement in throttle response, but, not necessarily more power. 52mm will more than likely give you some more up top, but, may reduce power at lower RPM. (at low RPM, power is all about flow velocity, not volume.)

Lower temp thermostat won't give you any gains. Might reduce spark knock some, but, if that isn't currently a problem for you..... then it isn't a problem. It MAY annoy the PCM though.... and set a code for engine too cold, too long. (PCM expects 195 operating temp. With 180 stat, it will never get there.)

If you run an SCT tuner from Hemifever, he recommends the 180 stat. Otherwise, just stick with stock.

 

That make sense about going to big on the throttle body, so I will go with the 50mm throttle body. The same goes for the thermostat, I will stay with the 195 degree thermostat.

 

You'll also get worse mpg's with a colder Tstat. Same goes for if you get an SCT tuner, and install a 180 stat. The SCT is pretty much all about power, not really for MPG's.

 

I'd say yes & no to that.

It depends on what else you've done, and how you drive it.
I've been watching my MPG as I bolt things on, and SCT was the single biggest MPG gain, if I drive mellow and don't hoe into the new found power.

These are the rough MPG numbers for the changes I made;
K&N +1.25
T'Fans +0.75
SCT +2.00
FI-Airgap, 52mm TB, 4 port injectors -1.50

Before any of the changes I was getting low 11's (with a slight plenum leak).
For a few months I was getting low 15's (still with the plenum leak), but now I'm mid to high 13's.
I can easily get back to low 12's if I revel in the new power I have.

I'm curious as to what the LT headers and 3" exhaust will do when I get to install that lot.

 

Initially, it is going to spank your fuel economy, because you will like the sound so much, you will want to hear it more. After that..... you *should* see a bit of an improvement, just depends on how you drive it.

 

Yup, that happened with the other mods also