I recently acquired a car that was originally a 2L and have been told the engine size has been changed to 2.1, which I have not checked yet? The engine currently has webers. Can I use stock d-jet FI if it is 2.1?

If it has a carb cam ...then it's no.

What you can do is use most of the stock d-jet components except the ecu, cold start valve and throttle position sensor and then add an aftermarket ecu, Megasquirt in my case, with a few newer sensors for throttle position and intake air temperature.

This can be done for as little as $500 if you DIY or as much as $2,500 if you have someone do the work for you.

As far as the injectors are concerned the 2 liter d-jet injector flow rate is sufficient to support almost 200 hp.

So if you can find out about that detail you have an answer. Yes, I have a 2056 running stock FI, but working around an aftermarket cam has been tricky. Impossible if the cam were designed to take advantage of the Webers.

The newer FJ67 injectors that are sold as replacements for the Bosch have slightly higher flow rates. I am running a 2056 with stock FI and cam with no issues.

If you're after a cheap option to try, you can increase the fuel pressure to the injectors by adjusting the pressure regulator. Probably best to install a pressure gage in there to what you're doing. Remember that flow rate is proportional to the square root of pressure to your injectors, thus is you want 10% more flow you need to increase pressure by 1.1 squared, or 21%.
Since you're only increasing displacement by 5%, in theory you'll only need 10.25% pressure increase.
Not sure just how much a stock pump is capable of putting out however, no experience there.

Tunable EFI is the way to go IMHO. At least look into it. . .