I did all of these cheaply with basic tools. try these if you have performance issues or hesitation then let the Knowledgable folk of Vectra C Forum help you if still at a loss.
£8.99 From Halfords
Sensor with a blue sticker and yellow tab. remove clean with care.
top view of the EGR valve, on the end is a connector remove to test.
I personally blanked as you can see here but you decide.
Vacuum Hoses 1m metre of hose like mine is roughly £2.ps i have 4mm on there at the moment but think the correct size is 3mm or 2.97mm to be super specific. but for 2 quid mine work fine for fault finding.
This is the BCS, for ease unbolt and you can remove the top over from the little black box attached. remove filter test if it helps either replace, clean or run it without the filter. choice is yours.
Injector 3, check the tab attached if yellow change. if not handy with electrics local VX should do it for £30-£40 which is nothing.
I have done all of these along with a sillicone hose set from DPH Motorsport and combined my car has been transformed.
these are a good starting point and learned how to do each of them from various how 2's on this site. im sure someone with better history of them will have the links to them but i will try myself to find and post shortly.