continuing on with my pi i have recently read a guide for dummies and in the guide there was a section on direct routing a pi product to a p2 facility rather than looping the p1 back to a storage facility first. Is this a efficient way of doing the routing, the guide seems to think so?
Always route through storage, that way if for some reason one p1 stops going to your advanced factory, the other p1 simply gets stored rather than dumped (for example).
Processors can buffer material for the next cycle. If your colony is perfectly balanced your basic processors could supply 20 units of each P1 commodity every 30 minutes to your advanced processor with no waste.
Real colonies are not that well balanced and the slightest imbalance means waste. [Edit] Supply of P0 will vary across the duration of the program so imbalance is inevitable.
There is also no cost to buffering your material. You need a launchpad anyway and each stage of processing reduces volume (except P4). Simply route P0 from extractor to launchpad to basic processor, P1 back to launchpad then to advanced processor and P2 back to launchpad.