2005 Subaru Legacy GT Manual Transmission - while on interstate, heard a noise and then felt like losing acceleration. Pulled off exit and lots of smoke coming out of exhaust. Not a head gasket - no lights came on, nothing rattling in motor, any ideas?

Question edited got clarity and remove 'hood speak'.
Question moved to model category.

The alarm system and engine immobilizer needs reprogramming. You need an auto locksmith or an auto electrician, or the dealership

https://www.google.com/search?q=2005+Subaru+Legacy+2.5+GT.+How+do+I+put+a+KEY+immobilizer+back+into+my+key+case

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Park it! You need to check fluid level and condition, before you do real damage.

Rear or front wheel drive on the '05 legacy gt? deavilleb

Interstate would be a MT-35 or MTP-35

Sears die hard would be a 35 series.

Basically any battery you choose you want a group 35 battery.

I think you should buy repair manual first for your vehicle after that it will be easy for you to solve the problem. Check the link may be you will find something useful here
2005 Subaru Legacy

Manual or auto trans? If manual, check fluid level. Grinding noise could be u-joint starting to fail, or even wheel bearing.

go have your catalatic converter checked, it may be plugged causing your car to suffocate when you accelerate

Try this site
http://carservicemanuals.blogspot.com/search/label/Subaru

I would buy a used Trans and fix the other one over time. That way you can take it apart and it might not take a lot of money to fix it. Then you can sell it or save it. Also you may look at the different trans to put in yours. Maybe a Legacy GT 6 speed. Good luck and have a great day.

here hope i found what you were looking for

http://www.devicemanuals.com/guide/Automobile/SUBARU/2005-Subaru-Legacy-owner%27s-manual-==TVRBNU9URTI=.html