Before doing any modding, sort your low boost pressure code. Also, get a BMW specific code reader. You could have other codes in addition to that one, plus other stored codes that might direct you to the culprit. Chasing P-codes from regular OBD2 scanners on a BMW is like trying to catch a greased pig.

No experience with the deletes or tunes, but others will chime in for that.

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2005 X5 4.4i Build 04/05 Maintenance/Build Log
Nav, Pano, Sport (Purchased 06/14 w/ 109,000 miles) (Sold 8/15 w/121,000 miles)

2006 X5 4.8is Build 11/05 Maintenance/Build Log
Nav, DSP, Pano, Running Boards, OEM Tow Hitch, Cold Weather Pckg (Purchased 08/15 w/ 90,500 miles)

2010 X5 35d Build 02/10
Nav, HiFi, 6 DVD, Sports Pckg, Cold Weather Pckg, HUD, CAS, Running Boards, Leather Dash, PDC, Pano (Purchased 03/17 w/ 136,120 miles)