Hello, when I did my vacuum hose job about 4 weeks ago, I didn't replace the ACV gasket (I sort of made my own because Mazda couldn't get it for whatever reason). Last week, I finally got the gasket from Mazda, installed it, and now have some problems. When I rev the engine under light throttle, everything works fine. When I drive it under light throttle, everything works fine. When I give it about half throttle, everything goes to hell. When I push the pedal down it seems like the engine stalls - my A/F goes really lean, and I only get about 3-4psi boost. When I let off the throttle, the engine speed drops and it backfires. It doesnt seem to matter what rpm range. I have tried opening the double throttle control manually, but didn't make any difference. Any Ideas ???
TIA, Chris H

 

Have you checked the MAP sensor hose?

 

MAP sensor hose looks good. Is there any way the sensor could just go bad, or any way to see if it is working?

 

First off, reset your ecu. It could be in limp home mode. You can the voltage check outlined in the shop manual, but that's probably not the problem, since it only started after you took the UIM back off If I were in your position (I've been there before) I would take everything back off and check that all the hoses and electrical connectors are routed properly. This could be a long shot, but if a hose to the fuel regulator solenoid got swapped with another that could make your engine run lean.