My 170bhp Ti was also down as a 136 Lusso on the DVLA, and so all insurance searches it comes up as a Lusso.
For my insurance, I stated that it was a Ti, and I enter the car details manually, not by my plate so I'm definitely searching for a Ti. It's pretty obvious if it's a Ti or Lusso aesthetically imo so you'd want your insurance to be correct.
Having said this, the place that I bought my car still thought it was a Lusso, and it was priced as one too! I snapped it up quick. It's most definitely a Ti.