You shouldn't have any problems to be honest. I was trying to avoid saying that they (the FSE valves) are a waste of money. TBH, I think they are, as has been said above.
If you're in that territory that then engine's running lean then uprated injectors and possibly fuel pump(s) should be done, thus rendering the FSE valve worthless anyway.
Even with high lift cams the air drawn into the engine should be well within the capability of the standard fuel system.
If, however, you were planning to fit some outrageously large turbocharger that can stuff 5 litres worth of air into a 4 cylinder 1.8 engine on each cycle then you would need a totally different system of fuel delivery anyway.
The old term was 'snake oil' when applied to magic additives. It may well be applied to these valve things. If the injectors can deliver the fuel adequately then there's no need. If they can't, then no increase in fuel rail pressure will help.
Most fuel injection systems can deliver far more fuel than the engine actually will ever need, at any point in the rev range.
Oversize injectors can cause problems as well - poor atomization, poor fuel/air mixing etc.