Your set up is matched and you don't need to change anything.We have had similar setups and when going to a bigger tube header and collecter found a slight drop in et and mph.If you were running a 2.30 or 2.40 intake valve and a 1.98 exhaust valve and over 540" you would benefit from the larger tube.One thing we did notice is with a heavy car a 16"to18" header collecter extension can be helpful.

Change mufflers. With small block I picked up 2-3 tenths going from those to pypes racepros, but any straight through muffler is going to be better.

I also run the 2-1/8" X 3" B/E Body Super Comps on my 528" Hemi in my 70' Challenger. I figured it was the choking point on my engine but it still made great power for a street engine. On spray they may be my limiting factor but I do plan on going to some custom bigger dia step headers eventually. I added themocouples & O2 bungs to mine for tuning while on dyno & in the car.

normally I run the 3.5 pipes w/bullets., I put these on for something else(can't remember what tho.)but decided to make a pass and was surprise at the et can't remember the mph.

3-1/2" Bullets on mine also.

I picked up 0.4 in the 1/4 in a well sorted mid 11 sec car by going from TTI 3" H-pipe system with 2 chambers to 3.5" x-pipe with straight through mufflers dumping before the axle...EFI took care of the jetting for me, lol.

While it might be quicker with a larger exhaust, is it worth it if it is a true street car?

Yes.

We run 2.125 TTI headers 1230 hp 5.0 on 26's at 142 mph NA 173 @ 8.0 1/4. 565 inches, 9300 rpm going thru the traps in the quarter.

Wow! That's bookin'! I think this answers the header question...

True dat.......wondering if it's can benefit from a bigger header?

I agree

My thoughts exactly. It is crazy fast, but has it ever been tested w/ a bigger header? I don't think I've ever seen an engine making that kind of power w/ that small a header on it.

IMO the OP's car is just fine w/ the 2 1/8" header and likely would see no improvement w/ a 2 1/4". The mufflers he's running are the restriction.

What's the collector size?

Obviously!