GMC SONOMA ENGINE POOR MILEAGE

I Have A 2003 Zr2 Im Getting A P300 Random Multiple Cyl Missfire Code And When I Got The Truck It Was Getting 21mpg And Now It Gets Like 15...

I Bought This Truck 4 Months Ago And The Fuel Mileage Has Gotten Worse. The Previous Owner, Who Is A Good Friend Got 19-20mpg. I Am Only...

I Have A 2003 Gmc Sonoma 4cyl-auto. It Is Underpowered And Gets Poor Gas Mileage For A 4cyl. What Kind Of Improvements Can I Do To The...