A few questions

Hi, My name is Jon Goodwin and i have recently bought a Gen 2 Turbo II.It has covered 30 000 miles since it?s production in 1990.Are there any components i would need to change at this current milage,and at what milage do problems normally start to occour?I have been on various RX7 sites,which have answered most of my questions,aswell as explained a few things. 1.How many people have heard of pre-mixing,and how effective is it?How many people use this method? 2.The boost cut is at about 8.5 psi,what is the boost limit of the stock turbo and what boost pressure can be safely run on the stock fuel pump,but with an adjustable fuel regulator? 3.What would the expected power output be whilst using a 3" single pipe system from the turbo with no cats and single exit pipe,hks filter ,adjustable fuel regulator and a boost increase? 4.If i were to remove the Air pump,will i need to replace the belt with a smaller one?ie,to run the water pump? Thanks in advance for any advise. Jon.