Copying this from my other engineering thread so bear over with me
Got it after 9 shots, so 27 tinkers in total.
After these many tries I was suspecting it to have some sort of pattern, at least for some tinkers. I decided to try it out to see if I was correct.
I would always get a tinker at 441-443, usually skill up on bolts and get either Synapse or a gulp, only once did I get one of the useless belt tinkers. Then I would get another one at 451-455 and again at 461-465.
EVERY single time I did the bolts I got synapse or gulp, no exceptions but the above mentioned.
When reaching 451 I would get either a gulp or a belt tinker and finally something completely useless such as another gulp or belt.
I did the first 8 re-levels with bolts only and eventually something flashy just to break the rhythm a bit.
By the 9th try I went for bolts up to 451 and then Ethers till the first tinker procc.
I happened to get Synapse as the first one which was allright.
I then did bolts up to 455 (seeing there's no tinker discovery) and then Ethers again and BAM, Tazik!
I continued with bolts and voila, a gulp.
This seemed strange so I decided (oddly enough) to re-level engineering.
I've now re-leveled engineering three times with the same combination of bolts and ethers and i've gotten the same tinkers every time; Synapse, Tazik and a gulp.
I don't know if RNG is playing a trick on me and decided to piss me down my back, or if this is a genuine pattern. Anyhow, it's worth trying out if you're willing to go for 'em.
Good luck