I don't think you can do what you want to do with the TBI system. All the sensors (vacuum and electrical) work together to make the engine run as efficiently as possible--with the least amount of emission problems. Start unplugging stuff and it'll just get worse.
Your best plan of action is to replace all the vaccuum hoses, change out the PCV valve and replace the EGR valve. Replacing the EGR valve may also involve cleaning the passage that crosses the rear of the head from the #4 cylinder exhaust port on the exhaust manifold. That task is a bit labor-intensive, but if it's your labor, no problem!
You might be able to get a rebuilt EGR valve from sarge at
morepowr|removethispart|@theramp.net.
You mentioned that sometimes it chugs and backfires... Take a look at the crank pulley - does it wiggle any? If so, you may have a damaged keyway/woodruff key on the end of the crankshaft. The symtoms of this problem is increasingly erratic timing.
It is also possible that the timing was not set correctly. There is a 4-connector socket with a cap near the battery. Two of the conectors must be jumpered together in order to bypass the ECM when setting the timing. The ECM constantly monitors timing and adjusts accodingly. When you are changing the timing, the ECM interferes with the process! Most aftermarket service manuals describe the tuneup process including how to use that connector to disable the ECM. You can find the Chilton and Haynes manuals at most public libraries. The Haynes manual may be listed as a Samurai service manual but also has Sidekick/Tracker sections.
Hope this helps!
