How to get PR4 in 3 weeks after you bought the domain

3 weeks ago we bought a new domain, hpcheap.com – google keyword tool showed that there are a huge number of searches (110k monthly searches) and there was medium competition. After creating the site and getting some links to it (from several PR4 and several PR3 sites), I was nicely surprised to see that google gave to hp cheap page rank 4, with nice PR3 for secondary pages. Also the associated twitter account, twitter.com/hpcheap get PR4. Usually, until now it took 1,5months to get at best PR3 for a similar site. Maybe is Caffeine effect, as SEO guru Mateescu pointed out. Now we must make sure it gets links also next months, otherwise it will drop fast to...