P1508 & limp mode
 

Having an issue with car going into limp mode on way to Thunderhill Friday. After about 3 hours into trip to Willows Ca from Reno, in 100 degree air temps car goes into limp mode at low speed after left turn. Pull over, cycle ignition off and restart car all is well again. About 10 minutes later making a right turn onto I-5 on ramp, happens again. Very hot weather, but car temps are normal for conditions including oil temp and oil pressure reading from added gauges. About 190 on water & 210 on oil. Continuing on happens again rolling down the freeway in a straight line this time at speed. Cycle key and carry on to hotel. Thinking this must be the 105 plus air temps and hotter asphalt having some affect.

Next day at the track car seems fine until 3/4 way around first lap after right turn. Same thing again. Restart car and exit track, go straight to BR racing tent.
After a proper scan code P1508 is read "Function monitoring Torque comparison"
It was suggested that the MAF was at fault, or the DME.

Never once did I see a check engine light, including the trip home after not returning to track. Multiple times this happened on the trip home, primarily after exiting a right hand curve and 2 plus hours into the trip.

2002 Boxster S with Cayman S air box & tbi, softronic tune. Been running this setup for several years with no issues.

Drove it again today after checking for any obstruction up to MAF. Cleaned and reinstalled. Much cooler at home today, still hot at 95. Somewhat lesser of any issue after every right hand turn again. Not full limp mode this time.

Any thought on where to look?

i'd say maf - probably the intake air temp sensor gone out of spec.

I have Durametric. Is there a number at idle or other I should look for?

no idea. i presume that the durametric provides iat info, but uncertain what format - temp, volts, %, ?

No more limp mode
 

Changed the maf, and it's a little better now. No more limp mode but still stumbles big time on accel. Primarily out of RH turns but not exclusively.

Unplugged the maf and same issue. Still no check engine light which seems odd.