Right now I have a regular performer, would the RPM be better for my combo? I'm wondering how much low end I would lose and if there is even a chance of performance gain.

355
882 heads ported pretty well
Performer intake
HEI, super coil, MSD super wires
650 spreadbore mech. secondaries
Hyper pistons 4 relief
Comp 268-H .454/.454 lift
hi flow oil pump
professionally balanced
unknown chevelle headers, 2 1/4 exhaust w/ flowtech Terminator mufflers

700R4
12 bolt 3.08 posi
295/50/15 T/As

It's a tough call. I think it would pick up your car a bit and since it is still a dual plane, not hurt the low end much. If you have a mild stall 2000-2500, I don't think it would hurt your low end at all. The reason I say it is a hard call is the cam is probably not making power in the rpm range (5500-6500) where the performer rpm intake is clearly better than the regular performer intake. If you have plans to add a bigger cam and better heads in the future, I say go for it. If you don't, it might not be a big enough gain to make it worthwhile.

throw on the rpm, i picked up 1/2 sec in the 14 with just that swap.

the converter is stock stall

i'd get a convertor first. about a 2600 stall would make ALOT more difference than going to the RPM intake. then when you have that, the RPM will help some more too. with a stock stall, i'd be surprised if you would actually see much gain in ET at the track, although it most likely would pick up some mph with the RPM.