What can cause them?

basically swapped Z4 ecu for a 6K ecu and have had inconsistent boost readings (i.e. 2nd gear accelerating 0.5bar then sometimes 0.8 bar, then sometimes only 0.5bar) then sometimes a Vtec style moment of 0.5 bar then going all the way upto max boost then fuel cut (none of this happened with Z4)

Car is a 93 wrx with decat ,full exhaust and induction kit.
Map sensor and boost solenoid were changed problem not solved BUT manual boost controller fitted and seems to have sorted it WHY?

Car was r/r and the 6K on one run showed a lean spot (i can get the dyno printout if neccesary).

Also the boost gauge when it gets to 0.8bar the needle wobbles slightly (this is with the mbc fitted)

Select Monitor was plugged in and would sometimes get a wastegate reading and sometimes not.Could this be a case of a dodgy ecu?

 

bump