Mac2411 - My current game in 2.92 Insiders (all settings maxed out but only 6 AI Civs) has 8 Precursor worlds that I have settled.  Is #7 below the precursor accelerator planet your looking for?

1) former site of exotic scientific experiments - Tech +1 Orbital Precursor Archive, +3 Pop cap, +100% Research, -50% Growth

2) has a massive array of Orbiting Relics - Sensor range +8 Orbital, +3 Pop cap, -50% growth,  +48 Sensor power

3) 3 vast Orbital Factory Rings - +3 Pop cap, +50% Manufacturing,  -50% Growth, +20% Pollution

4) Prison World - Orbital Prison (crime -10%),+3 Pop cap, +150% manufacturing

5) World completely converted to a Refinery - Orbital Refinery w/ +0.1 Promethion, +3 Pop cap, -50% growth, *30% Pollution

6) Constructed from Durantium asteroids - Orbital cloud (+0.1 Durantium & +10% Kinetic attack), +3 Pop cap, -50% growth

7) Built from Crystalized Promethion - Orbital Precursor Accelerator (moves +1), +3 Pop cap, -50% growth

8)  Carved from a fragment of a Thulium world - Orbital Moom (+0.1 Thulium & +10% Hit Points), +3 Pop cap, -50% growth

Here's the changes from the 2.92 Insider changelog - 

Map Generation  

• Maps will generate a more satisfying layout and create better player positioning   

• Optimized the amount of time it takes to generate a map  

• Slight increase in the number of sectors a map can generate  

• Increased overall map size  

• Fixed hyperplane cluster connection  

• Increased single sector size