HO25 heater resistance

[dwelch09]

got the ho25 heater resistance bank 1 sensor 1 last code summer. went ahead and replaced both sensors (up stream and downstream).could not clear the code. kept coming on after trying to clear it a day or so later. went ahead and just drove it until last week when i noticed a stumble and the check engine light flickered. hooked up my autoxray and got the code for what was the number four plug. i replaced the coil pack and thought that would also take care of the ho25 code. not so but the other code p0304,cylinder 4 misfire cleared and the stumble went away. while waiting for the coil pack to arrive i checked the plugs and they all looked like they were new. gap was on the money also. this engine runs great and has ran great. would like to clear that ho25 code. some say maybe a vacuum hose leak. soon as the weather warms up i'll go under and try to check the vacuum hoses where ever they are located. anybody know what to zero in on for the fix? are there vacuum hoses under there? thanks Denny the code is p0053