[91 Buick Roadmaster Wagon]

I have TBI too and I have the same question and have not seen anyone coming up with a remedy because most people here seem to focus on smaller cars.

Therefore, I have been asking myself this question for about a year now. I believe for similar reasons, GM probably abandoned TBI in 1996 since they were required by law to have OBDII that year and one of OBDII's functions is to follow the mpgs. I've been fortunate to find the G-Series vans made in 1996 over 8,500 lb to have TBI, but I have not been able to confirm that 100%. If these vans have TBI with OBDII, then maybe we can just convert our OBDI TBI engines to run OBDII and then buy a scanguage II? Anyways, I'm still searching and trying to find the answer.

Another idea and probably a cheaper and better alternative is to install a different fuel injection system. I know for a fact that the Tuned Port Injection, TPI, run more efficient with better fuel economy and more horsepower than the TBI anyways. Plus, the Corvettes that used TPI during the 1980s and early 1990s had mpg gauges on their instrument cluster, a confirmation that going this route has a promising possibility that the mpguino will function perfectly.

The TPI units fit perfectly on 5.0 and 5.7 Chevy V8 engines. I wonder if anybody has done a mpguino gauge on a TPI engine now?

I posted two pictures a TBI engine and TPI engine to compare.

By the way, I believe I may go with converting my car to a TPI and add a 6 speed manual transmission for sake of saving more fuel with higher gears and less parasitic demand on the engine.

But before doing so, I will explore other ideas on different drive-trains that yield the best mpg vs costs to make the conversion. I have been researching the 2.4 Ecotec 4 cylinder engines and Mercedes Diesel 5 cylinder engines that are possible to fit inside a Buick Roadmaster Estate Wagon.