Sorted my issues with a few restarts...
I had a hard time thinking what to replace in my garage... From the Top: Type Z, Carbonizarre, Cheetah, Phoenix, Monroe, 9F Cabrio, Tailgater, Roosevelt, Dubsta (unmarked model) and finally the Adder.
Replaced the 9F eventually, for the Jester - which is a really superb car when tricked with exterior mods - handles very well too. I found the Turismo a bit... lacklustre - seemed to accelerate slow and I'm almost positive the Jester has a very, very slightly higher top speed (tested by seeing how much air is got from the same jumps at top speeds) although the cars dynamics and physics could affect this.
I did, however, want to complete the Grotti/ Ferrari collection. I did have the Stinger GT at one stage, replaced it with the standard Stinger, then lost by somehow "accidentally" selling. Don't know what happened there - must've been really baked. I think - although it's rare Online - I'll get rid of the Dubsta next. Want to keep the Phoenix and Tailgater due to rarity. I also had a hard top Manana at one point, but got rid for the Dusenberg limo.
Oh, and that messing around with having the pack installed but not seeing things online, has removed my Thompson SMG/ Gusenberg Sweeper. So don't know if I should be arsed about that (was it really any good with the low accuracy hip firing - even with short bursts) or whether there'd be any way RockFailStar can re-add it to my account.