First thing is don't take advice from the wanker who "educated" you about greys, it's complete bollocks, all tuners were using these for donkeys years before siemens even existed, no one has as of yet shown any difference in delivery that produced a different result in power/torque, or if they did I've missed it, greys are perfectly fine, however they are no longer made, and so any spares will start to dry up also, so a new kid on the block like siemens might be a better bet, can't see this becoming a problem for around 10 years or so.
99.9% of bad problems are due to the mapper, or mismatch of things, like your last engine for example, on those cams/turbo, std compression would have given far better off boost driving, the sudden kick that you feel is because there is nothing much there to start with, ie it's lost a lot of power off boost that it could have had there.
I'd have kept the std exhaust cam BD8, and run a BD15 inlet if you want.
I'd go for std comp, T34.48, keep your greys, unless you need to change, if wanting around 360-380 I'd keep the std cams, although a BD15 will certainly help upper power immensely with a small loss at bottom power.
I run greys, T34.48, std comp, std cams, boost starts around 1500/1600, full boost by 2600/2700, so it's not so on off, mine is mapped and on different ecu.
What ever you do I'd say you would be silly NOT to get it mapped, it really does make that much difference, when I was on "off the shelf" chips it was good, but never realised just how little bottom end it had, compared with afterwards when it was mapped, honestly like getting out of a 1L car into a 2L car bottom end wise, of course as it produced so much better bottom end, the big kick had gone when turbo came in, there's still a nice kick, but it doesn't have as much deficit to make up for in power now as off boost there is so much more, it doesn't increase by as much as before, still the same end figure, real life driving it's rapid with instant/ish boost.
As a comparison to my last chip before ecu swap, it now makes 23 bhp more on 10psi less boost, and it's not chronically overfuelling now either, can only assume they pulled the timing back shed loads on chip for that to happen, but it must be said it was a bad chip.
My car passes the mot on 1.7% CO, but it could be leaner just make it a little lumpy whereas now it's perfectly smooth.
The best money spent would imo be on mapping, whatever the spec, since mapped I have more off boost power, more on boost power, masses more mpg, better emissions driveability, but depends what YOU want power wise.
I picked up well over 150miles to a tank more range since mapping, but was a very bad chip with 10.3 AFR on lean cruise!!
I need to have bottom end as will be towing a caravan, NOT NOT at 40mph everywhere though!!
tabetha