I have a 93 base model, A/T. The problems I am experiencing with the car are:

When car is held at a constant RPM while driving, it shutters and surges, like the fuel flow is not steady. I replaced the O2 sensor and it didn't help. I am wondering if it is an ECU problem. The stock ECU is marked as remanufactured.

Also, I installed a boost gauge and it never gets above 6 PSI. Possible vacuum leak?

I am open for suggestions. Should I invest in a stand alone ECU like the Apexi or will those even work with the A/T? Or is there possibly a cheaper suggestion?

 

Does your boost gauge also read vacuum? If so, what is your vacuum reading at idle (as well as what is your idle RPM)?

Obviously, the car should not behave in this manner in stock form. Before you start replacing ECU's or other parts, get the problems sorted out first.

You might be better off just taking the car to a good rotary mechanic and have them check the car out so you know what you are dealing with. The name Garfinkle has been thrown around this forum a lot and he apparently is located somewhere in TN. Here's the number: 615-893-4469

 

The vacuum reading varies from 20-15 at idle. The idle also varies, sometimes it is barley above 500 rpm at idle and other times it is somewhat normal at about 750-800rpm.

The only mods so far are a K&N air filter in the stock air box, aluminum radiator, aluminum AST tank, and Raven muffler.

The guy I bought it from also set the turbos up as non-sequential. Does that affect the boost readings?

 

Non-seq would definitely affect the boost readings. In non-seq form (also called paralllel) they turbos basically function as a laggy single turbo, and there is no transition. You should see little boost up to about 3000rpm, then a slow build to a max of 10 at about 4500rpm.

Garfinkle is in Murfreesboro (sp?) TN, and from talking to him on the phone the guy definitely knows his stuff and can definitely help you out.

As for your issues, when you say the vauum varies, do you mean all the time? Does it jump in the 15-20 range all the time? Is the idle stable? Or is it sometimes 500 rpm and stable, and sometimes, 900rpm and stable? It vacuum the idle is jumping and bouncing, that would explain why the vacuum is varying, but if the idle is stable and the vacuum is varying, that'd be a good indicator of some sort of internal engine issue.

 

When the idle is about 500, the vacuum is around 20 and when idle is around 800, the vacuum is around 15.

 

same issues here, bucking and low boost but I am running seq with only a downpipe and intake