Is this the cam?
http://www.iskycams.com/shop/index.php?main_page=product_info&products_id=936
If so, you need a lot more cam to make torque past 4000.
That duration number is "gross" duration. We need the numbers at .020 or .050" to really know the deal when you do find a gross 280-300 degree cam, hopefully in the .450-.490" lift range. (I don't know how much lift your springs and piston/head combo can stand)
Also agree on a possible restriction, but that is a very mild cam.
Here's IPD marketing pitch on it: https://www.ipdusa.com/products/7389/100823-volvo-street-performance-camshaft-b18-b20-ipd-100823
this model has a broad power band starting at 2500 rpm up to 6000
I may have used on waaay back in the day, can't really recall. I have used a couple of VV81 cams: http://iskycams.com/shop/index.php?main_page=product_info&cPath=127&products_id=937
And they're pretty sporty feeling. They're a little listless under 3000 rpm, they really kick in at around 3200, and on my engine, pull hard up past 7000 rpm. It's so productive to keep it in the lower gear that I often run it up to 7500-ish, it's still pulling harder than it would in the next gear. (Ahem, probably why I'm taking the PV's motor out again - apparently not a great idea to spin stock parts that fast - but at least the failure mode hasn't been catastrophic so far)
And in practice, that 3000 rpm thing isn't much of an issue - just rev it high enough in each gear to be over 3000 in the next gear. And it's really not feeling all that flat under 3000, probably more power and tq than the stock motor had at that rpm.