Well I guess I’ve got all bases covered..got 5 eBay EKPs AND a ET3 unit..I think the good news is that the EKP on Z4 E89s is bolted to a metal bodywork structure in the boot (trunk)…so heat conduction plus convection much better than other E series cars?I got the stg 2.5 lpfp with walbro 535. I've read the 525 is harder on ekp and that the 535 draws slightly less amps than 525 pump.
They're the same ekps just different amazon vendors I believe. Et3 ekp is the only one that's been physically upgraded. Now how much longer will et3 last compared to the others idk. But For the price of et3 stg 2 you could buy minimum 7 if not 8 $50 eBay ekps, Which seems to last for many people with upgraded pumps about a year.