I use 4 of these and I get good throughput, but they tend to be costlier.
http://www.amazon.com/gp/product/B00IBPLI48/ref=ox_sc_sfl_title_3?ie=UTF8&psc=1&smid=ATVPDKIKX0DER
You can also install another pvc pipe with smaller diameter inside the main pipe. Also make sure the electrician leaves an...