need help with 951 performance problem
 

The 1986 951 is new to me as I just came over from the 911 side. Here is the issue: Sometimes when I get into the throttle it runs like it should and when the boost comes on it pulls hard. Other times (even on the same drive) when I get into the throttle it feels like a normally aspirated car and the pull from the boost is never felt. I just installed a stage II chip set with banjo fitting and now I can actually see the anomaly on the boost gauge. At equal throttle settings sometimes the boost only goes a little past 1 bar and other times the car pulls hard and the boost is at 2 bar. The engine does run smoothly and idles fine, it just seems like a NON turbo car at times. What could cause this intermittent loss of power???

sounds like its going into 'limp mode'
when this happens, the KLR computer which controls the cycling valve. limits boost to 1.2 bar (absolute) on the guage.
turning off the car resets the fault.
Check all hoses, especially the hoses and connections to the cycling valve. Its the white, 3 port valve under the intake with the 2 wire plug.
A faulty throttle pos sensor will also trigger this fault.

go here
http://www.lindseyracing.com/Merchant2/merchant.mvc?Screen=CTGY&Store_Code=LR&Category_Co de=TECHGARAGE

for
more info on extracting codes

Thanks form the help, I'll start looking there.