First like said probably vac leak. The pcv valve needs to be a Ford only one. The others leak thru. The IAC on the 2.3 goes bad quite often. Can clean. Carb cleaner not brake cleaner.
Check the EGR valve for leak thru. Can cause bad idle.
The throttle position sensor needs set at approx .95 volts at idle give or take a little
Look at hose from vam to turbo needs spring in it to prevent collapse and no holes in it.
I assume looked at turbo to intercooler couplers. Sometimes they have holes or not put on correct. No insult meant putting that intercooler on bottom one can slip and you not see it.
Compression test or leak down test. The 2.3 turbo is bad about blowing headgasket. Mostly between #3 and #4 cylinder. If so check head for cranks.
Now for vacuum diagram. New Page 1
Lot of good tech on there faq and tech pages. NATO - North American Turbocoupe Organization
Always could make a boost tester. I have a front mount intercooler. I thought leak free until I made one and found several. Keep the psi below 10psi. The thing will come off and if so please get out of its way. I didn't. No harm done. I was very lucky. IC Pipe Tester
Hopefully I hit it somewhere if not just ask. One of us should help you out. Maurice
1989 Mustang 2.3 turbo, rebuilt SVO motor, 88 computer,vam upgrade, adjustable boost control, intercooler, c-4 trans
, 7.5 345 turbocoupe rearend, motorsport driveshaft, Black interior.
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