How accurate is Desktop Dyno2000?

It is not too bad IF you can get the airflow of your heads and enter your camshaft.

Dyno Sim (the new one) seems to have much better tools and has flow files for some aftermarket heads (AFR/ED) as well as many camshaft profiles. It is comparitively VERY expensive though.

I think they are both a bit optimistic, but you can use the information as one part of your decision.

FWIW
 
i have desktop dyno and found it to be relatively close. my car made 213hp and 268tq at the rear wheels with no tuning ( i was really rich) and DD said 327hp flywheel with no accessories. factor in some losses for the accessories and drivetrain and the numbers are close.