The whole "longer trumpets make better power" is a very sore point amongst some tuners/mappers anyway - I've seen pretty good evidence (back to back tests on a car) that proved you can make just as much power/torque on shorter trumpets with a good map
If you are talking F4r when you say that shorter trumpets still made the same power then it must have had a problem with the map on the before for it to have not dropped torque after.
but then people like 519 have said the opposite
Danny is completely correct about that, anyone saying the opposite to him in this instance in terms of torque figures on an F4R simply doesnt know what they are on about.
TBH a few lbs/ft here or there isn't going to make that much difference
By the same token, no mods you do to an F4R are very worthwhile unless you are going FI then, as just about all mods people do to these engines only make small gains for each mod.
My 90mm trumpets just about fit with the slam panel in place - but there's no room for a filter. If you could be bothered to get some curved 90mm ones made up that angle down slightly that would work too
No filter is great for performance but not so great for reliability, lol.
Ultimately there is a relationship between intake length and where in the rev range it is optimised for, so for out and out power shorter trumpets are not a problem generally as shorter trumpets work better at higher rpm and thats where you will be making peak power by definition on these sort of engines.
The problem is though that the short AT Power ones are so short that you'll probably find they are optimised essentially for about 12000rpm, so going longer isnt going to lose you any power at the sort of revs that most people run, ie only into the 8s at most, and what it will do is gain you torque.
With the F4R engine in particular, due to its unwillingness to rev, it really is a case of longer is better, with some other engines thats less the case.