so here's some info on the PureTurbo upgrade for the 535i!
Hi Gene,
Your turbo is different than the 135/335 turbo but we do have our STG2 available for your vehicle also.
First thing is no more 89, these engines crave octane so if you want to run pump gas only you need the highest octane you can find(91/93/100
. JB4 is the easiest to tune on these vehicles. The stock fuel system is fine until you want to run higher quantities of ethanol. The higher the octane the more boost you can run and the more you will get out of the STG2 turbo. High flow cats or catless downpipes are another upgrade we recommend to get the most from the turbo.
-Charles
Operations Manager
PureTurbos.com
353 Airport Road
Oceanside, CA. 92058
(760)721-7669