I had a similar setup (JDL 4-2-1, Stock OP and FP) with the Invidia R400 - was great for a few years when I was doing more city driving, but over the last few years with a move, if I am driving for work/pleasure, it's been all highway.
The combo was boomy, drony and fatiguing overall right in that sweet spot at 125-135kph. The catback on its own was great, but as soon as you add a header onto these cars, you need to be much more careful with exhaust selection.
I ended up reinstalling the OEM catback - it's a night and day difference. I can actually hear my own thoughts on the highway now! I do miss the tone of the Invidia a bit for sure, but having a much more comfortable highway driving experience is worth the trade off - if I get bored of this setup I may just go with a mild axle back like a Fujitsubo Authorise S.