I've stripped down a K series before, so if I blow it up I can fix it again
so anything is good! I know some people have turbo'd them, don't think that'll happen though
I'm not bothered about how much I spend - I love the car to bits and it never fails to amaze people with the ride quality and speed! So anything really.
Ok, while I'm not going to get involved too much in some of the sniping, it would be remiss of me not to point out a few modded car facts.
1) A modified slow car is almost never comparable to a standard fast car. It can come close, but there will always be something unless you get really daft with the mods, whether it's a lack of structural rigidity, a lack of low down usability or even just that certain spark. If you have the choice, the standard fast car is nearly always a better way to spend your money and go fast.
2) You haven't mentioned whether your car has been remapped to take the engine mods into account, if it hasn't, especially as you've changed the cams, I'd be very surprised if it's producing the 150bhp you're claiming. 140-150bhp is possible from a K series, but they are fairly highly strung to start with. Going back about 7 or 8 years, I had a modified 214 (the older shape), that was running different cams, ITB's, exhaust, and had been fully remapped, and that only just broke the 140bhp at the fly estimate, and it wasn't as reliable as it could have been, it would have benefited from a full rebuild and lining to get that.
Now, with those out of the way, on to ways to move forward.
Firstly, don't touch the engine (possibly barring a proper remap) any more until you've made sure the rest of the car is up to it. Most people don't mod engines for more power if they don't plan on using it, so look at brake and suspension upgrades. This is especially relevant if your concern is how it performs against other, faster as stock, cars.
Apart from ITB's, other options you could consider are a turbo kit, or an engine swap for a turbo. If you decide to stay with the NA route, ITB's, a rebuilt, balanced and lightened engine, getting the head at least ported and polished (you can swap it for the head etc from a VVC engine if you want) and so on.
You could also play with *** if you aren't too worried about the risks of killing it and the short term only power availability.
Lots and lots of options, just not that many truely sensible ones when it comes to modifying cars.