Anybody know how to regain a bit of back-pressure on straight pipe exhaust?

Its a considerable straight pipe, still have the cats on just no muffler.

About 2.25 inch pipe used to replace the stock "Y-Pipe" basically comes in the same format as the stock do, they meet under the front dash part of the passenger seat but do not connect as a "Y" and they both face down just under the passenger seat.
Obvious that much of the back pressure is lost, how would we be able to regain that pressure without adding a Muffler. Still want it to be a considerable "Straight Pipe".

 

Not a great idea for motor longevity. Just my .02

 

Think this effect the engine in the long run?

 

not sure if back-pressure is beneficial in any sort of way on a 4 stroke.

the guys that made the engine in the picture are lots smarter than me and it doesn't look like they gave two shits about having back-pressure. looks like they were trying to keep it minimal to me. . . . .

on 2 strokes, backpressure was a side affect of acoustical tuning; not acoustical as in sound quality to the ears, but using sound waves to "pulse" wasted fuel back towards combustion

 

The cats create all the back pressure needed for whatever you think backpressure is needed for.

Scavenging is a function of tube length. It's why headers are often built to be equal length tubes, and why the collectors on open headers are various diameters and lengths.

In my drag racing days (well before computer modeling) we'd install collector extensions on a car and make passes. Cut off some extension and make more, repeat till we figured out the optimum length for that particular engine build and car set up.

Sometimes you had more low RPM end results, sometimes in the high RPMs. For us, the overall ET was what mattered. For anything else, the use of the vehicle is what matters.

Grunt or top end?

Problem is, most folks with streetable vehicles want it all. And reality says every choice you make is a compromise of something else. So, know what you want to accomplish (and why) then pursue that.

As Rock says, boost fixes more than dinking with I/H/E bolt ons, particularly on modern, fairly efficient engines.