Good point on the carb spacers. I added a Phenolic 1" tapered spacer and it made a noticeable improvement, especially on the low to mid range acceleration . I then added a 1" open spacer under that and noticed even more improvement.

When I tested my 540s with different cams, intakes and carbs there was always an improvement with spacers. 1in was better than none and 2in was better than 1in. The only caveat to that was that with the last combo even though the 2in added about 5-6 hp at peak the 1in had a broader area under the curve so I stuck with the 1in.

Haven't seen that intake in person. I just dynoed a 565 w profiler intake, it came within 15 hp of what dyno sim showed ( 865hp), I just dynoed a 555, had flotek 375 heads, claimed flow about identical to the profiler heads, calculated hp also in the 880 to 900 range, was off the mark by 100 hp, had a BMP 4500 intake box stock. Customer had no interest in trying spacers because he had no room in his car vs hood scoop anyways but compared to most other similar motors I have dynoed I can about guarantee there was 20 hp to be had from spacers and box stock bmp/merlix x ports vs cncd 375 heads at 1.625 vs 1.82 and 2.375 vs 2.54 , Im going to assume hp was lost there but customer had sent intake out for nitrous plumbing and wasnt taking it back off to try a different one or mod it

I would have liked to compared my chinesium intake that i outperformed a edelbrock super victor with to this merlin/ bmp. I dont think when you have heads that flow 300/320 cfm and motors turning 5800 that there is a ton of difference between most open.plenums as long as you give it as much spacer as it needs to straighten out air flow, add plenum.volume. now, bump ci up to 565, turn rpms up to 6500, buy heads that are supposed to flow 440 cfm, then any intake thats not perfectly matched to the killer heads is going to hurt combo/hp by knocking that flow waaaay down

Yes, 565 w profiler 375 heads. profiler intake, 1250 dom modded by norm to flow 1400+ , was close to what dyno sim showed at 865hp (compression though was not ideal at only 12.8 because it was originally built to spray with nitrous)
555 w flotek 375s, merlin x intake box stock except a bunch of nitrous lines plumbed on manifold and slight port obstruction from nitrous tips, box stock 1250 dom, also had only 12.5 complression becuase again was built to be sprayed, it actually calculated on dyno sim at about 900 hp, missed its mark by a mile at only 780. afrs were in the mid 11s, if you leaned it out intio the low 12s it made 760 hp, bsfcs were terrible for compression motor at .460 to .540 on top, the 565 had bsfscs in low to mid .400s, .380s even in some spots, it made all kinds of power leaning it into the high 12's while tuning.
customer was unwilling to try a different intake or even carb spacers on 555 so in the end did the box stock merlin kill power, did the flotek heads not flow what they were claimed, just more questions.
In our MARINE world, a 540/565 with pretty much any open plenum intake, especially one with a dominator where throttle bores are spread out versus tight in midddle wants a intake with some plenum volume and transition from flange to port openings if its not built into the intake already, hence carb spacers picking up both tq and hp without much negative effects IF you have hatch clearance, Smitty

With all of these spacers it seems like we're just getting back to the venerable tunnel ram.