Just installed the GRP cold air intake on my 400 and wanted to share my thoughts:
1) It's a fairly straightforward install with the most difficult part being removing the bottom part of the stock air box. Trick here is to temporarily remove the left trunk strut and unbolt and move the S/C coolant reservoir (and disconnect the return hose) and it comes right out
2) It's a VERY tight fit and it makes contact with the engine coolant mount, factory roll bar and clam. The nice thing is there is foam to protect the areas that make contact but the fit is incredibly snug … honestly might be better to go with a slightly smaller canister for a better fit. You really have to jam it in and push/bend the coolant bracket to get it to fit. You also have to make sure you push the canister as far in towards the throttle body as possible … as it will interfere with the wheel liner if you don't
3) The stock airbox is VERY restrictive with TWO air paths that are open all the time. Looks like they removed the vacuum actuated flapper for the 400 for more air flow. I suspect this dual path is what causes the throttle blip issues (quick blips ie. heel toe causes engine to bog rather than rev up) coupled with the ECU.
4) The stock airbox is also VERY large and heavy coming in at 5.1 pounds. The GRP intake weighs only 4.1 pounds so you get a whole 1 pound of savings
5) The results ………… are positive, you definitely hear the induction noise and supercharger more … and most importantly, it does help mitigate the throttle blip issue. It's not perfect but it does help 80% I would say … so very noticeably better! Throttle response overall is much better and power feels about the same as I already have the Komotect 460 kit with headers, decat and tune.
All in all it's a good upgrade if you are looking to fix the throttle blip issue and get a bit more induction/supercharger sound. And the extra 1 pound of savings should net at least 0.5 right?