Yes i used the factory spring. The more you tighten the spring the more pressure it takes to close the waste gate. I have not tried to push it to see how much boost you can get out of the factory spring but there is still a good bit of adjustment that could be made for guys wanting to run more boost.
1994 F350 4x4 ZF-5 7.3 IDI Turbo. (SOLD AND NOT LOOKING BACK)
1993 ext cab 3500 4x4 6.5TD 360,000 (SOLD)
1985 K10 6.2 banks TD (SOLD)
2000 Turbocharged WS6 TA 524rwhp 498Torque (SOLD)
2001 LQ9 IRON 409, T56, 9 inch, 471rwhp 450Torque (SOLD)
2005 GSXR-1300 (SOLD)
2002 2500HD LB7 4x4 (PPE valve, MBRP 4 inch, AFE stage 2, Profab horn, EFI live) (SOLD)
2002 3500 DRW LB7 4X4 ZF6
1985 Toyota PU 4x4, Solid axle, 35 MT's, duel lockers, 5 speed.
Last edited by cbr600rx7; 12-30-2009 at 10:54 PM.