T28 Hybrid Escort cosworth

Usually sits and holds 1.3bar.... Got the car back on the road it it seems to want to hold about 1.6 bar

So obviously turned the boost down a few screws, but ive turned it down way to much and in 5th gear it only holds about 0.7 bar. So it needs turned back up. What im wondering is the car usually holds 1.3 bar in 3rd and 4th gear, but in 5th now it seems to want to go off the gauage, would a boost controller solve this problem and keep it at 1.3 even in 5th gear?