you sure you got spark? swap plug wires. Or even yet if you do get to th einjectors to pull em, swap them around also, see if the prob follows the linjector or not. a 2.5 is only roughyl 13 percent bigger than a 2.2. I really dont think it would casue a problem at idle. Hopefully in your case it does but.............Also start/crank the engine over with the valve cover off, You could have a "slow" valve, meaning it isnt following the cam correctly (partially sticking) causing a loss in Compression when it runs. Just a couple of ideas. I imagine you will keep us posted.