Portugee420

So here's the story... I let my little bro borrow my SC400 while i dropped an engine in a sweet mpg saver i picked up for his graduation (95tercel) pics soon** lol.. So to get to the point he was putting 87 octane gas instead of 91octane... he didn't know... so i showed him the big sign over the fuel guage...lol lessoned learned :chairshot: ... my mpg is drastically low and slight misfire on cold start, almost seems like the cheap gas fouled my spark plugs, cars current mileage 243,xxx and running strong :)but notto its full potentional.... (HC 2 below state max on smog test) don't want to ruin the catalyic converter...probually did already but hey thats the Nature of The Beast ^Thanks Cali^ Basically tired of the distrubutor style ignition want to know if anyone has swapped a newer 98-00 sc400 upper half. for instance 95 sc400 4.0l block, upper end/intake 98-00 (DIS 250hp to 290 hp) or knows any swapped done maintaining factory used parts/look but making 300hp+...or atleast over 250hp.. since i do have access to Toyota/Lexus parts/info looking to do a Factory Swap...no mickey mouse wiring and scratched parts.. thanks for reading and info will be greatly appreciated..

I ran into somewhat the same issue... my engine/trans. ran fine, fluid levels set and ok,no mil,my drive shaft bushing/coupler assy worn/torn, trans. mounts worn, replaced trans. mounts and "dampner" located on rear of driveshaft. drained and re-filled diff. fluid and road tested, vibration still there, worse when OverDrive Disable was disengaged,re-inspected vehicle on hoist, found rear differential assy (spider gears) causing abnormal vibration/shudder even with eng/trans. ok/ no mil on, after replacement of rear differential carrier assy, (upgraded final gear ratio 3:55) car rides like it was brand new.. hope it helps to solve your current issue and/or help anyone else...my works done..lol