You'll want to determine where the time is being spent. You can trace the BW side to see how long it is taking on that end but it is probably the design of the report that is taking the time. Are you using a UNV universe going to a BEx query or a BICs based connection?
Query Stripping is automatically on for BI 4.0 SP5+ for BICs connectivity. There are also a number of optimizations that can help improve performance in the newer Support Packages.
Determining where the bottleneck is is the first step.
thanks
Jb