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Got the Walbro GSS342 - that is a bit long (5mm) for Busa - can fit it though. But GSS342 fits perfectly to ZX-14, so we swapped pumps with my friend, he had Bosch 0 580 454 032 which was a bit short for ZX-14 but fits perfectly into Busa. Both won ! That Bosch is for a 450HP Audi, so I guess its ok for an all motor Busa The Bosch flows at Busa std pressure about 180LPH (measured) which is exactly the same as Walbro, even both manufacturers claim 250LPH. No filter, just plain tubing with adjustable regulator and 13.7V. Walbro takes about 14A to run, Bosch takes about 8A to run. The Walbro has a flowby valve which activates around 4.5-5bar so you can not run it higher than that. Walbros flow at around 4Bar is significantly better than Bosch - anyhow Bosch blowby valve activates way higher up in pressure so it gives more adjustability for pressure.Due to the installation easiness (only electric connector change and one white pastic piece cut) I would choose Bosch over Walbro again.Then about the the stock pump. We measured 115-120LPH with std pressure, 13.7V. That is a very good flow figure. Anyhow it has one very interesting feature: At around 4.3bar the flowby valve is activated so you can not adjust pressure above 4.2bar without loosing pressure completely. The Busa stock pump in question is from K5 and manufactured by Mitsubishi.When modifying the stock busa regulator with stock pump, around 4-4.2bar is absolute maximum. After that you start to loose the pressure because of flow by valve getting activated.I am just wondering if the flow numbers are in line with others ? 180LPH vs 255LPH is a big difference. Have not checked that at which pressure the 255LPH was promised...EDIT - When thinking now afterwards, I am pretty confident that we used 2.8bar instead of 3.0bar and did not check the voltage. We assumed 13.7V which is the spec for the power supply we used. Need to redo some of the tests just to confirm these points. Also the appr 14A for Walbro but only 180LPH indicates that there may be some serious restriction in the testing system ?EDIT2 - Disregard the above flow figures, we just remeasured the testing system and confirmed that test system was accidentially set around 16V. Anyway the Bosch figure measured earlier and according to the manufacturer are 120LPH@5bar, 150LPH@4.3bar, so based on that Bosch is good for around 400hp@crank depending on voltage and injectors. I guess that Walbro flows around 160LPH@5bar. More importantly we need to measure the running voltage at pump in bike to be able to have more exact testing numbers.