94 SE only 15-17 MPG.

Is this normal or too bad?

I feel my car lost some power after I changed sparks, because I felt the accelabrate from stop is some bad than before. Is there any way to check if I installed all sparks right?

Thanks

Are you getting a check engine light? What brand of plugs did you buy? You could hook up a timing light to each spark plug wire to ensure that you don't have a wire issue and/or that the plug wire is firmly seated on the plugs.

i'd say replace your O2 sensor

im only getting 250-260 a tank and i normally get about 290-310

Sounds like its time for agood old tune up. Spark plugs, wires, air filter, fuel filter, pcv valve, 02 sensor, change em all, you will see a diffrence there. I get about 19.
Dont use Bosch!

I would say that is way low for mileage. My 94 SE gets 27MPG regularly. Right around 400 miles every tankful.

Damn it, I did bought the Bosch. Is this very bad choice? What kind band is better?

I have Bosch wires in my 93 and Bosch plugs and wires in my 99 and never had an issue with either car. Many on this site don't care for Bosch, however, I've personally never had an issue in the 30,000 miles I've been using Bosch parts. Most will recommend AC Delco for the 3800.

Even using Bosch parts, I still get about 400 miles per tank out of each car and have noticed no power loss.

My 3800 killed a set of Bosch plugs, and good ones too, paid 6 sumthin a peice, unfortunatly I had changed the spark plugs day the after I bought the car, May 10th 2003, and if you look on my sign up date it says May 11th 2003. About 7 months ago I removed the bosch and tossed stock AC Delcos in there.

Could a colder plug (1 range) help with milage at all? I'll drop down atleast one when i get my hot cam / rebuild, but if it can help... What about with an engine in tip top shape, with a CAI (boxed and all), what are the milage/performance gains?

Unless you are accelerating hard routinely, 16 mpg is really low for these cars. My '92 SSEi did 24.6 mpg on the last fillup and it has 124K mi on it. I'm using 93 octane premium which costs me $2.04 here in Ames. I don't often stick my foot into it. 2/3 highway -1/3 city miles. The car has no mods.