I've seen this issue mentioned here a lot and thought I'd throw some info out there that maybe not everyone is aware of. In Mar of 91 Mazda put out a service bulletin concerning hesitation between 3500 and 4000 RPM. It affected T2 and there were a couple of fixes. One, if you went into a dealership within a certain time frame, they would replace your ECU with a new one. The other fix was to install a 2 MM orifice into the wastegate acuator hose. It is Bulletin No.
009/91 date 03/22/91. It affected:
1989 JM1FC3 K0700000-K071200
1990 JM1FC3 L0800000-L0808000
1991 JM1FC3 M0900000-M091310

 

Got the info here:
www.alldatadiy.com

 

my 88 n/a is having that problem. at 3k.

 

do a search for 5th and 6th port actuators. if its not that. check the tps