Note: This answer is invalidated for the OP who may not have been deported at all but it still answers the question actually asked and may be the most helpful for others.
ECB4.3 Deportees
An applicant who has previously been deported from the UK at any time
must apply in writing for a revocation of the Deportation Order and
wait for the outcome of the revocation request before they can travel
to the UK (if a non-visa national) or before applying for an entry
clearance (if a visa national). An application for entry clearance
from a person with an extant Deportation Order will be refused
automatically. Entry in breach of a Deportation Order is a criminal
offence under section 24 (1) (a) of the 1971 Act. Any leave acquired
prior to the Deportation Order is invalid.This also applies to any European Economic Area (EEA) national – for
more guidance on these see EUN1.3.
So it seems that you won’t be stopped at immigration as an EU citizen but you would be committing a criminal offence by not having the deportation order revoked first.
Border guards are not supposed to ask any question to EU citizens and, as a matter of fact, I have never been asked anything when entering the UK. There are many reasons why your past problems are not really relevant now, one of them being that as an EU citizen, you are entitled to work in the UK so you cannot work illegally anymore.
When you enter as EU citizen you use the UK and EU passport lanes at the airports and often you can even use a self service booth.
As you did not get a mark in your old passport, and the visa agency told you not to apply, I am sure you have no reason to be handled any other than any other EU visitor.
Credit:stackoverflow.com‘