Are IQ tests "biased" against individuals with Asperger's Syndrome?
Depends which IQ test you use - individuals with ASDs show a typical "pattern" on the WAIS, which can cause it to appear like they have lower IQs. When tested with tests which aren't biased in this way, they appear to have the same IQ range as neurotypicals.

The assumption that those with an ASD are cognitively impaired pervades both popular and scientific literature - those who are minimally verbal or non-verbal (i.e. those who do not show fluency in their speech) are often labelled as ‘low-functioning’. The characteristic cognitive profile shown by the WAIS is commonly interpreted as a unified deficit known as ‘weak central coherence’, the tendency to focus on low-level details as opposed to the higher-level ‘whole’ (Happé, 1999). Much of the recent research regarding the neuroanatomical signature of autism relies on the untested assumption that cognitive strengths of autistic individuals as shown by the WAIS are nothing more than low-level by-products of high-level deficits. Dawson et al. (2007) have shown using Raven’s Progressive Matrices (Raven, Raven, &amp; Court, 1998), a complex yet general test of intelligence, that the WAIS severely underestimates autistic intelligence (by an average of 30 percentile points). It is therefore recommended that though the WAIS has a number of useful psychometric properties which can be applied in the diagnosis of autism, it is not used as a measure of intelligence in such populations.

References


Dawson, M., Soulieres, I. Gernsbacher, M., Mottron, L. (2007). The Level and Nature of Autistic Intelligence. Psychological Science. PDF
Happe, F. (1999). Autism: Cognitive deﬁcit or cognitive style? Trends
in Cognitive Sciences, 3, 216–222.
Raven, J., Raven, J.C., &amp; Court, J.H. (1998). Raven manual: Section 3.
Standard progressive matrices. Oxford, England: Oxford Psychologists Press.