It’s just a pump gas street car...

For what it's worth, my car is 3740lb with me in it and has been ~142mph.

On SINGLE 4" exhaust... let alone dual.

It does seem like the dual 4" should be enough but it for sure worth unhooking it and giving it a try.

So was mine. But when its at the track, it's quick and easy to swap a pulley, mix in a couple gallons of race gas, take out some timing, and let it eat. But hey, its his car.

I have the 4" Dynomax bullet mufflers with a full 4 inch x pipe system to the axle. Again, like others, I was surprised how quiet they were, disappointingly unloud

I think this is correct. 6 lbs of boost is what the factories use on the stock engines to keep them out of trouble. My Cummins will make 26 lbs and it's a stock 12 valve with just some minor pump tweaks and a single 4" exhaust. I know diesels are different but come on, 6 lbs?

Turn up the wick and let it eat! Might require some tuning though to reach the full potential.

If the kids 360 can run 9.55/141 at 21lbs. The hemi at 13-16 boost lbs, Ye haw. Its all about conservative timing. More boost makes more power than more timing.
Doug

Turn that 12 Valve up. My stock 12 valve has been over 35 lbs for 200,000 miles.
Doug

I turned it up to 10 lbs with improvement.It sepatated one of the slip joints.Will uncork it and see what happens At South Mountain Raceway in July!

The last blown pump gas hemi I dyno tuned made 927 HP at 7300 RPM with 7 lbs. of boost with 33 degree timing, it was 12% undriven.
We swap the pulleys so it had 13% over drive, put in 110 octane race gas, reduced the timing to 25 degrees and that motor made 1024 HP at 6500 RPM with 12.0 lbs. of boost before going into detonation above that RPM We added two degrees and it went into detonation sooner I should have started with 22 degrees or less, probably
What I found out later is you can make to much power on the street, even with pump gas normally asperated
Back pressure can make a heck of a lot of difference on some cars based on the pipe and muffler sizes and type used

If I have a 4" collector going into 4" pipe,does it matter if the cut out is after the collector or after the "X" pipe? Would going after the "x" have any benefit??

https://www.youtube.com/watch?v=Qv0Mmqwz0lw

I believe being after the X with cutouts has no benefit at all, just adds a slight bit of back pressure.
How much pipe after header flange and before X?

If you have enough for the engine to "see" a 14-18 inch collector extension then dumping out, I think that would be optimum.

Just my thoughts.
Love your car btw.

Thank you.I wonder if collector length makes a difference with a blown application.Zoomies might work best but I street drive....alot!

I think the principles remain the same when we are talking about these power levels , temps, exhaust speeds etc.
I would think someone, somewhere, has done dyno testing with blown motors and collector tuning- finding that data might be an interesting quest.

It wont matter at higher boost levels but in street trim with 6 to 10 lbs boost it might be worth playing with .
Might pick up a little tq .
more boost and rpm- I think its just about getting getting exhaust out ,least amount of back pressure.

In your case, Im thinking the X pipe isn't helping and getting the cutouts in front of the X just eliminates back pressure/turbulence.

Just my thoughts.