The difference is negligible without the duct.
One thing is without the duct your engine bay will be noticebly dirtier. However, with any DCI this becomes more apparent anyway.
I'm sure if your browse the for sale threads that someone out their has a stock duct, actually referred to as "snorkel" on this platform, at times.
If you have any questions about the injen let me know that is another feasible option for a cleaner look