[Wings of Fire]

The NE-α parasite, but it was never a T-103, it was a completely new model of Tyrant.
The NE-α Parasite was only added so that Nemesis could retain some intelligence, hence why it can use the rocket launcher.

What I linked clearly states the biological base of the Nemesis was the T-103. That's from the ResiWiki. How about more evidence from Project Umbrella?

By administering an artifical parisitic organism to a B.O.W., it could enhance the B.O.W.'s abilities greatly, and its brain would also be controlled by the parasite. This was the "Nemesis Project", a completely original biological transformation technique advanced by the Umbrella Europe Sixth Laboratory in France. After transplanting the "NE-α Type" parasite into the spinal cord of the new mass produced Tyrant (T-103 Type) at the cellular level, it devoured the t-virus cells in the creature to reproduce, and formed an independent "brain" around the medulla. Meanwhile, the parasite also eroded the creature's central nervous system and destroyed its frontal lobe, then linked the rest of the brain functions to its own brain. Through this, the host's entire neural network was changed. Nemesis had taken complete control of the host's mind and body and enhanced its intelligence and susceptibility to suggestion.

A chemical known as "VT-J98" was necessary for the cultivation of the specimens, and stock of the solution was ordered from the Umbrella sales office in Raccoon City. 4 In addition, there was an interesting report about the original test specimens. During the process of cultivating Nemesis-T, some specimens attempted to escape from the facility. This example showed that the intelligence of the specimens had been vastly improved, and also showed the danger of a new intelligent life-form which could rebel against humans just like other developmental B.O.W.s. As a result, a specially-designed protective coat (similar to the "limiter coat" featured on the T-103 series) was wrapped around the specimens to limit and detract their power and prevent them from going out of control and rebelling.

Normally I wouldn't give a shit, but saying 'You're wrong' and not backing yourself up when I quote evidence irks me.